Billed incorrectly repeatedly !!!

Nashua Mobile with MTN service upgraded my contract without my approval. I am getting charged for voice and data which i did not request. I have a blackberry top-up contract with BIS and airtime. A contract that has BIS DOES NOT NEED DATA !! WHY AM I BEING BILLED FOR DATA WHEN IT IS NOT REQUIRED. I have emailed and called customer care regarding my account. Every month my bill varies and increases drastically not in my favour. When i took a contract i knew i had a set amount on month to pay, i work on a budget and don't see the need for my TOP-UP CONTRACT TO HAVE DIFFERENT AMOUNTS. I want feedback as soon as possible i have tried to keep this under wraps and just kept calling but i no longer have the patients for this anymore so i put it on hellopeter. I went into the store and called the store as well but i was told it will be queried. it was queried and then still went incorrect of my account again. I am not 1 bit impressed with MTN and would not want anyone else to join MTN especially if they work on a budget because they according to how they want to and don't require authorisation. putrid from a service provider