Overbilling and incompetence

I have a phone contract with MTN that I have been paying R319 and I decided to get a router and sim which was R199 router and R30 for sim monthly but from then I have been paying a different amount which now adds up R733 I have been sending emails and till this day I'm not getting assistance the two employees that are in charge of this are Pulane Seutloadi and Hlaysani Zitha they offer you a certain deal and make you pay what you didn't agree to they ***** from customers and MTN employers let them as their superiors does nothing about it I really need this to be sorted out