Not true.
End of the month or whenever all networks will meet and balance their Interconnect sheets. In some cases networks make a profit in some cases they break even meaning no one pays no one. In other cases that network who made a profit the last time round now needs to pay the other network and so forth.
That being said let's use another example:
I have R 300 pre-paid airtime. I will still phone and finish up that R 300 pre-paid airtime no matter what the reduced rates are. I'll just be able to use it more frequently. It will still be used and the netwrok will make a profit on that. With or without the reduced rate.
Pitbull i do not know what MTN's average income per call from their subscribers is - let us assume for the moment that it is R3. Assuming this gets decreased to R2.70 I challenge you to calculate the impact on MTN's revenue and then find the cost in MTN's financial statements that will have a corresponding decrease.