bad service

I was given a call from Summer mobile which is a dealer partner for MTN and told to do my upgrade with them. I accepted and they added an amount not disclosed in the conversation. Remember I did initiate this upgrade. Now it more than 4 months and I have asked MTN to resolve this issue of which nothing has been done. Every month my subscriptions are paid for yet my phones get suspended. Today it is suspended yet my account subscriptions are paid for, of which I sent my proof of payment. why is services from such big companies so bad.