incorrectly billed

I recently received my contract statement from MTN on 07.04.2015 and to my surprise the amount reflected on the statement is a total of R545.00 whereas my original amount is R391.00, when I further check my invoice it shows that the amount of R211 is billed for was Packet Data Calls ( of which I have no clue what this is and have never been billed for this, since I first got the cotract in Sep 2013 ). I initially got this contract with Nashua Mobile before MTN took over. Since this move to MTN It has been a nightmare with regards to account billing and other services. Just recently I sent a request via email for my phone to be softlocked once it reaches R391.00 however this was not done and i keep getting these ridiculous bills and what makes this whole experience even more unbearable is that when attempting to contact MTN customer care I am faced with call centre agents that hang up the phone on my ear. This whole takeover has just been so unbearable and has left me with a sour taste. Had I wanted to be with MTN in the first place I would have gone to them ******.