Sorry for my ignorance, but have checked the whole site on this matter. Do you know,how are working incoming roaming calls( step-by step)? I mean, how come that there can be incoming roaming for free? :umm:

It's simple. Wholesale roaming rates are dirt cheap, pennies. Most countries charge a hefty surcharge to call a wireless phone (e.g. 25c/min). Wherever country X's wholesale roaming rate is less than country Y's surcharge, there's an opportunity to make money. So you take a tiny country, like Liechtenstein, It can be covered with two cell sites, few customers to pay for those two sites but a huge opportunity to make money as a roaming operator.

For charged calls, the profit margin on incoming calls is about 90%, so wholesale is pretty cheap. And don't forget that the SIM network still gets income for the received calls - ie from the charge on the person calling you. Also, I suspect that the negotiation with visited networks may not include mentioning that there will be no outgoing call revenue to share, as they all use callback. So these small networks probably hardly get noticed when roaming.

So the SIM network probably figures it can waive an incoming charge of 5 or 9c per minute, and carry it in the outgoing charges, but the reasoning slipped up when people had the idea of separate callback

Thanks for your reply. I agree with what you wrote. I heard another explanation. Most of operators don't charge incoming roaming call up to 5 seconds. So your provider does sent some signal to network, where you do currently roam, that you have new call every 4-5 seconds. So basically you should have uninterrupted series 4-5 seconds calls until your call is finished.

It's an interesting idea, but I would think it's a bit unlikely. If your network was doing this, they might soon be blacllisted for cheating out of paying for the calls

I think most likely is either that the wholesale cost is 3c or 5c and they waive it, or possibly that they have made an agreement with all the roamed networks about it; this latter one seems less likely, as why would an mvno invest all the time to make separate ageements than the parent network. The key arrangement will be the balance between this parent and the virtual network, about how they share the incoming revenue, whether incoming call charges are waived at this stage in return for whatever slice of the charged calls made

Bear in mind that an MVNO is an operator so it is paid to terminate calls on it's network by other carriers before it then sends the call out again so there is a balance to be had bettwen incoming revenue and outgoing cost - not smoke and mirrors, just plain economics... :)