MTN keeps taking your money for nothing!!!!

I have a mtn customer since 2002 with 3 contracts. 3 years ago i cancelled the one contract in the mtn shop after it had expired, so i thought ok all done, guess what? Walked into a mtn shop to upgrade one of my other contracts and found out that for the last 3 years they kept charging me the full contract price of the contract that I cancelled in the shop. I was upset R30000 they took from me!!! I asked the lady in the mtn shop how its possible and what they going to do? her answer was" nothing we can do about that, the other lady that you cancelled with never past the information on! So again from the mtn shop in Herm**** we phoned mtn and cancelled again!!! 2 months later mtn phoned for a upgrade on my one number , again the lady told me that i still have 3 contracts!!!!! I asked her how? she sid it was never cancelled!!! i did the cancellation personally on a mtn phone in the Herm**** branch! So what now? is it legal to keep *****ing my money???? Mtn you suc**** People please be aware of what they do to you. I am now going to see lawyers to get out of this MTN mess.