Termination Charge….
Why do I have to pay more to call from one network to another?
Most of the tariff’s we see in for mobiles/fixed lines are with different costs to call “with-in” the network, outside network mobiles and then fixed land line.
This is because of a charge called the termination charge. Since we follow the “Calling Party Pays” principle, every time we connect from our operator A to a operator say H, A needs to pay H some part of the charge levied from us for the call, as rights to use a part of H’s network to access phone in H’s network. This is a strictly regulated charge since if it were a free market, very un-ethical strategies can be employed. Even now, the part of the cost that is passed on to the customer has only an upper limit and interesting strategies can be employed 
This charge exists in VOIP also, as the termination charge paid to the non-VOIP network that forms that last part of the chain though which the data is routed and this is why VOIP is not as cheap as it seems to be.
