We don't know that the Greek network is allowing free incoming calls. They probably still receive the revenue, but you haven't been charged it by your network, who are balancing it against the fees they receive from people that call you, and they hope to earn from your 'outgoing' calls too.

It may be that some of these mvno global SIMs have done their own direct roaming deals, but I don't necessarily believe that despite what Travis says about his influence on CallKey's arrangements for two years. If they'd promised in return a share of outgoing call revenues that turned out not to exist, ie because callback is an incoming call, then they'd have been rumbled by now

That is very easy.
The french user dials a german number.
The phone call gets directed to the T-Mobile switchboard in germany - then forwarded to SFR to terminate the call.

Chris

This was a pretty unusual agreement at the time, and (as someone at Viag Interkom once explained to me) part of it had to do with a lawsuit between Viag and Deutsche Telekom that Viag seemed likely to win; Viag offered this as a solution. In other words, Telekom didn't do this willingly, and it wasn't the result of government effort to open up the market. (I don't remember the exact details of the suit offhand.)

In this case the originating operator would be T-Mobile.

UM pays T-MO for the use of their network at rates set by T-MO. T-MO connects the call to your wifes UM number and pays UM a termination fee for doing so. UM then connects a call to the Greek network on which your wife is roaming and pays the relevant termination fee which is covered by the termination fee which T-MO pays to them. Your wifes free incoming is actually funded by your outgoing call charges.

As mentioned in another post, they aren't, it's just that the revenue that UM receives on incoming calls is enough to cover the cost of terminating on the Greek network. In the case that the origin of the call is also UM - then you have the following breakdown for a 5 minute call (forgetting VAT because that would just make it even more complicated);

You pay UM 2.20 EURO for the call (5 x 0.39 + 0.25)
UM pays T-Mobile 1.25 EURO for a call to another UM mobile (5 x 0.25)
A portion of that goes to UM for the termination fee, lets say 1 EURO (5 x 0.20)
UM then terminates a call on Vodafone Greece paying 0.60 (0.12 x 5)

So that's 2.20 - 1.25 + 1.00 - 0.60 = 1.35 EURO profit.

Obviously this is an example because I don't know what T-MO charges UM for using their network, also other networks have higher termination charges than those in Greece and we haven't taken VAT into account.

In part because DE T-MO demands a higher profit due to higher operating expenses (such as maintaining a radio network) and in part because they'll charge what they think they can get away with.

That's just the way the networks operate. When an SFR user dials your German number, the call must pass through T-MO even if the call will eventually loop back to the same network.

No, they just see that a call is made to a T-MO DE number and so passes the call to T-MO DE.

That kind of information is not stored on the SIM.

It would usually not be possible to fall into a negative balance because you have one of the following scenarios;

1. Inbound calls only - your home operator will disconnect any call that exceeds your credit

2. Outbound call using IN - the call will be disconnected when your credit reaches zero due to the real time billing

3. Outbound call using USSD - the call will be disconnected when your credit reaches zero because the call was originated by your operator, similar to callback.

4. Outbound call billed to a credit card - there is little risk to the operator, so you'll be able to make calls as if you are a contract roaming customer.

There is also the possibility of near realtime (warm) billing whereas there may be short periods where it is possible to fall into a negative balance due to the delay in update of billing records but I doubt many operators if any rely on this, due to the risk.

Unobtrasive the 0,12 euros that Greek mobiles earn is only for calls originating from inside the country. And only from companies that have a direct link with the mobile operators (only OTE and q telecom had this some time ago now more).

Calls originating from other sources (e.g gsm-ways, abroad) are not bound to that charges but to other lower (depends on agreements)

In regard to the issue we are discussing the answer may be that there is some sort of mutual agreement that each of the providers offers free incoming. Eg. When I roam with my UM card in Greek (say in TIM) I do not pay for inbound and whenever a TIM customer roam in Mobilkom in L. he does not also pay for inbound.

How about this;;;

It would seem to me that TIM-GR (example) is giving up a very lucrative revenue source (charging for inbound in FL.) FL has what? 20 K inhabitants who would roam in GR while GR has what? 10 M, who would roam in FL? Not very "fair and balanced" I would say.

ALSO, we know for a fact the DE T-MO (example) prepaid charges 79 ecents / minute EVERYWHERE to receive a call outside Germany, yet they allow UMers to receive free inbound in DE. Some there IS no reciprocal agreement between those two countries. The same (no agreement) is probably true for most major countries (FR, IT, GB, ES, GR, etc.)

I don't think your suggestion is a vaild reason. Sorry.

Stan

There was somthing similar with Meteor (1800) in Ireland and the two 900 carriers (O2 & Voda). Meteor got some sort of ruling that they could have the right to roam on the 900 MHz carriers.