MTN's failure to remedy my contractural concern

I took out a new contract from MTN. I asked the agent to give me a new comparative contract in-line with my existing one. I assumed all was okay until i ran out of anytime minutes. I contacted MTN as I felt the contract was unjust as I was sitting with hundreds of MTN to MTN minutes which expire and I now have to fork out for extra anytime minutes at my cost, whislt I lost financially for the already paid MTN minutes. How exactly does MTN know which network my contacts belong to? What if non of my contacts belong to an MTN contract and all my calls are other network based? This minute split by MTN is theft and is a means to force the user to purchase additional minutes, all while being paid in full for the expiring MTN minutes. I got one reply to my email, to which I further rep**** and since that I have been ignored.