Fed up with MTN's in ability to help me.

I bought a phone on contract from a MTN store since I bought it's not working properly it doesn't make any calls I had it now for almost four months I pay every month for a phone that can't make any calls since I got it .I pay monthly but don't even get the data and airtime I was promised but yet I pay even more then what was agreed upon. I have send them a mail been to their store and yet nothing has been done about this . I am fed up now with their inability, their incompatibility to do their jobs . I wish for someone from hello Peter to please contact me then I will tell the rest I really need this sorted out now .