Yes, that's the same idea, but with the ability to choose different outbound trunks based on the dialplan. The one disadvantage of using a different SIM card for each country, compared to a single international SIM card, is that you would need to redirect the inbound PBXes trunk whenever you changed cards. This would be invisible to callers, but it means finding an internet connection every time you change location, which is something of a pain.

After lots of trial and error, I did finally figure out how to remotely change call forwarding on the free version of PBXes, i.e., to get call following. So this would make it possible to give friends a single US number (or whatever other DIDs you obtain), and to use that number to reach whatever SIM card you put in the phone. Both incoming and outgoing calls would be at VoIP rates, plus the cost of a local call on a local SIM chip.

looks great but very complicated.

I would still prefer pbxes using callback.

Reason is simple. If you buy local prepaid cards you think that you get a good deal, but for example here in europe most simple prepaid cards do charge a minimum of 0.20 euro per minute.

If you would have a united-mobile card you can make a callback using betamax for around 0.10 to 0.15 euro per minute. When doing this in roaming free countries it's cheaper than a prepaid card.

When in countries where the there is no free roaming you could indeed use callthru.

This just saves you buying all different sim cards and keeping track of them.

It's possible to do that without pbxes. Just point the DID to the SIP address of the provider chosen to forward the call.

There are an increasing number of mnvo providers with cheap int'l calls from a few cents.

But if they don't list good rates for all countries, or for calls to the same country, then callthrough via a foreign access is worth looking at.

It may indeed be that callback has similar rates, but sometimes just pressing one or two buttons to dial a saved entry seems a bit easier

I don't intend to actually use it; I'd just like to figure it out. As someone said in another forum, if I count my time, I've got my costs down to only a couple of hundred bucks per minute. ;)

Seriously, when you say you prefer "pbxes using callback," are you referring to the callback feature of pbxes? If so, I don't believe that is available in the free version.

In any event, what I'm proposing does not preclude using United Mobile or any other card. I can set up pbxes so that one DID rings whatever cards and/or landlines I choose, a second DID allows me to change those target numbers remotely, and a third DID provides callthrough dialtone using any of several cheap outbound trunks (maybe there is a way to do this with fewer DIDs, but I haven't got that far yet). The only cost would be the outbound trunk, which is often free to landlines, plus the cellular connection which is often free inbound. But the system would work the same for both international and local cards.

I do agree with your point about buying and keeping track of lots of different cards. Any savings are likely to evaporate once the minutes expire.

I tried this with IPKall and VoipCheap, but for some reason the forwarding didn't work. A call to the DID rang the VoipCheap softphone, but, if I recall correctly, I always got a busy signal when I tried to forward the VoipCheap line to another number.

I wonder if it's more to do with IPKall settings, as this works fine with UK DIDs I use. And if the softphone is online it will ring both this and the forwarded destination, the latter starting a few seconds later. Have you tried Freedigits?

What I do is create an extension on my handset. I've got it programmed into Fring and into the Nokia SIP phone. Fring works ok over EDGE. Using either wifi or EDGE I program in a co nditional call forward once I get the SIM. EDGE is usually over a contract SIM for two minutes before I swap SIM cards.

IPKall offers a free DID, and nothing else -- i.e., there is nothing on its website for sale, no customer service, etc. I think it then just forwards the call. There is very little to configure. Perhaps VoipCheap doesn't like double-forwarding from IPKall. I know there was a period where the Finarea companies were blocking pbxes, apparently because a pbxes subscriber tried to set up a callback business using pbxes and a Finarea company.

Anyway, I don't mind using pbxes to do this. It seems to work just fine, and it offers some flexibility. For example, you could set up a Ring Group so that the DID would ring all of your SIM cards simultaneously. Then you wouldn't have to bother with remote forwarding.

I do have a Freedigits account, but I also use it with pbxes. It's the DID I use for remote call forwarding.