AT&T GoPhone SIM Compatibility Issues
 

Hello everyone.

I just went into my local AT&T store here in Chicago and got a GoPhone prepaid SIM card for use in an unlocked, dual-sim, quad-band phone I picked up on focalprice.com. (Link to phone)

The phone works fine with my ekit SIM and I can connect to AT&T network fine with the ekit from my house.


I am having problems with the GoPhone SIM, however. It appeared to work OK in the store in the unlocked phone, but when I took it home I couldn't get the SIM to solidly connect to the network.

By "solidly connect," I mean that I can't really make/receive calls consistently from it. I was able to get a text from AT&T and at one point was able to connect to customer service via 611 before the call dropped--but that's it.

I put the SIM in an old unlocked Cingular phone, however, and it works fine. I can receive texts, make/ receive calls fine.

I called AT&T customer service and the official line is that there is no guarantee that the goPhone SIM will work on non-AT&T phones. I was told that it may work sometimes and at other times it may not. This seemed to correspond with my experience.

I was wondering if anyone else has had this experience. I was thinking of heading back to the store to swap out the SIM, but I am not sure if it will matter.

I had thought that if you had a generic unlocked GSM phone that the goPhone SIM was supposed to work. I am trying to figure out if it is the SIM or the phone.

Thanks!

The first thing I would ask you is how the phone works on AT&T with a different SIM (such as TMO or a foreign SIM roaming on AT&T). It sounds like a phone issue, though the dropped calls and unreliable service will be familiar to a lot of AT&T users, especially in urban areas.

Have you tried sticking it in the other slot of the dual SIM phone?
 

Have you tried sticking it in the other slot of the dual SIM phone?
And how well does the ekit SIM work in the slot of the ATT SIM?

A couple of other suggestions:

1) You may want to pick up an old 2g or 2.5g AT&T or Cingular sim chip from a dealer or from an ebay merchant and see if it works better. If not, just use up the airtime and toss.

Why:
The firmware/hardware of mobile phones made primarily for the Asian market (with more limited overseas exports) tend to work better with 2G (GPRS) or 2.5G (EDGE) sim chips. Putting in a 3G (HSPDA) or 4G (LTE) sim chip *may* work in some handsets, but performance may be erratic. That's despite newer sim chips supposedly being backwards compatible. Explanations of different standards are here: GSM - Wikipedia, the free encyclopedia

Have no problems with my old 2G Beyond GSM/Jolt/AT&T sim chip, my Tuyo/T-Mobile sim chip or my Digicel Bermuda sim chips in the USA (the last two I think are 2g or 2.5g). But the 3G dual IMSI ekit simplecalling sim chip is tricky in my two multi-sim chip Chinese phones. It will work in the first two sim slots of my quad sim phone, but causes phantom phone reboots in the last two slots. So I always keep the ekit sim chip in one of the first 2 slots.

2) When can't place a call with AT&T, try turning the phone off and turning it back on again(if all else fails, pull the battery as well). That may re-authenticate the sim chip on the local mobile telephone switching office. Also another trick is to dial *777# for a text message balance check so AT&T has to look up your account, that sometimes will also set things right. Or do a network search, select at&t and attempt a forced registration. But just turning the phone off and on seems to work the best.

I posted in your thread in Howard Forums. You've got some good suggestions. Also, as I already mentioned, verify that the phone's IMEI is the one active on the sim. Those goPhones will only work with/lock to the phone used to activate the account, for a certain period. Did you use this phone to activate the goPhone sim?

I bet the problem is......your phone is only triband. At&t uses the 850 band in most places but you can pick up sporadic service on the 1900 band.

YEah
 

Thanks, everyone for all of the help.

I am beginning to think that my problems are a combination of cheap Chinese phone + crappy AT&T coverage.

I have done all of the things people suggested--put the AT&T SIM in the second slot, tried my ekit SIM and forced it to connect successfully to AT&T, turned it on/off, tried (unsuccessfully) to check the balance via *777#, the phone is (supposedly) a quad-band, had AT&T Cust. Service activate the IMEI with the SIM.

After I posted initially, I went to a location about a mile from my house--which is where I experienced these problems--and was able to use the phone pretty reliably from the other location.

I didn't initially think it was a network problem since the GOPHone SIM works perfectly in my ancient CIngular at home, but not in the new Chinese phone.

The only reason for getting the AT&T SIM is for a trip to Mexico I'm taking in the next couple of days. It will be interesting to see how the setup functions while roaming in Mexico via the Telcel towers.

GadgetKen's explanation of the 2G vs. 3G chips is interesting. Does anyone know if the 2G or 2.5G chips are still sold by AT&T. I'm wondering if I can just get one at the store?

Thanks everyone for the great advice!

I will post a followup about what happens with it in Mexico.

An older Cingular/AT&T 2G sim card would look like the pictures in this ebay ad: NEW CINGULAR / AT&T 64K 2G SIM CARD Buy-It-Now-> $6.48 - eBay (item 290504788175 end time Dec-02-10 19:10:40 PST) Note their ad copy mentions Treo 650's have a similar issue rejecting the 3G cards.

An AT&T company or affiliate store might have one hanging around. Worst they can say is "no." Can't guarantee the 2g vs. 3g card issue is what's causing your service issue, but it's a possibility.

Do bring your old AT&T gophone with you to Mexico since you know it will work with your existing 3g sim card.

Enjoy your travels south of the border!

I will not call it crappy AT&T coverage. This certainly sounds like, as already mentioned, your phone is NOT quadband. It's missing the 850 band that AT&T uses heavily.

My experience with my supposedly quandband dual-sim chinese phone is that, ONLY sim slot 1 on my phone has the 850 band. The sim slot 2 almost always latches onto tmobile regardless of the sim I put in it. I tested it with a number of reaming sims I have. When I put my AT&T sim in it, there was barely any signal.

Interesting theory. I have the same four-SIM phone that gadgetken has, and I notice slots 3 and 4 seem to park on 1900 MHz whereas slots one and two park on 850 MHz. (I'm in Saskatchewan, Canada, and the only 2G coverage here is Rogers), so it's entirely possible that slots 3 and 4 in my phone lack 850 MHz. A person would have to go somewhere where a carrier has 850 MHz but no 1900 MHz coverage to know for sure.

Interesting, Bossman & akraus -- So the places where I CAN get AT&T coverage with this ostensibly Quad Band phone means that it is picking up the signal on GSM-1900?

It will be interesting to see what happens in Mexico--if wikipedia is to believed, Telcel uses 850 for 3g and hasn't rolled it out yet in the area where I'm headed.

So, theoretically, I guess, it should connect via GSM-1900.

Does anyone have any leads on reliable dual-sim quad-bands? I may try and do an exchange/return with focalprice.com if i have bad luck in Mexico.

I travel down there a lot, and many of the places I normally go around Mexico City are in Telcel 3g territory.

Suggestions for dual sim phones
 

Have had good luck with a dual sim quad band MFU V200 phone. Simple features, works well, very sturdy. Very basic though with a camera/video camera, MP3/MP4 player, FM stereo...no wifi, no alphanumeric keyboard, no TV, no touchscreen. But it does the job.

For a phone purchased from the US, lowest risk would probably be a Beyond E-Tech Duet dual sim phone. Only maker I'm aware of that has dual sim phones that are US FCC registered. You could also try before you buy at a store. Can be bought from several dealers including: Search Results for duet phone at JR.com They also have one of the lowest SAR ratings of any phone officially sold in the US: Other manufacturers cell phone radiation chart - CNET Reviews

In Mexico the 1900 band will work great. 3g is a newer techbology, so wherever the have 850-3g, they have 1900-2g.

Side note: you cannot call with the att SIM in Mexico to any place other than US/Canada/Mexico.

Yeah. Let us know how it works out for you in Mexico.

I actually also activated a couple of AT&T prepaid sims (one goPhone I bought for $1.25 on ebay and one regular AT&T sim I had laying around) for use when we go to Puerto Vallarta, Mexico, in a couple of weeks. Mainly for the $0.25 rate for incoming and outgoing calls. The goPhone sim will ONLY work in the phone I activated it on. I certainly do not anticipate any problems in Mexico since I will be using regular quadband/3G smartphones.