MTN IS CHARGING ME R259 I AGREED ON R239

I've been trying to get a resolution to my queries 2 months now. Does MTN take their customers seriously or not?I have paid BEEN BILLED WRONGLY I UPGRATED MY CONTRACT ON THE 07 NOVEMBER 2015 AND I SIGNED THE CONTRACT OF R239 PER MONTH BUT IM BEING BILLED R259 WHILE I HAVE THE COPY WITH ME **** too in order to be manipulated into a direction less beneficial to myself. I do not get any valuable response from anybody other than saying they will resolve, but nothing happens. Everybody says they will get back to me but nobody ever does. I cannot believe that any management of any reputable company will allow this to happen. I have been to the stores twice , I have contacted customer complaints, AND they drop calls in my ear, I cannot believe this WHAT IS WRONG WITH MTN? Please can anybody tell them thier service sucks . I need my issues dealt with please. I want a resolution as a matter of principle. If I must evaluate my time and resources spend so far. This is beyond ridiculous. I challenge anybody to resolve this!<br>