Stop ****en debiting my account

I've had a contract with Altech since 2013 and my subscriptions were about R364pm. I never used the sim card only the phone. I got an SMS in Oct 2014 stating that my balance was over R7000. I immediately called in to report the sim card as ****** and the agent blocked it, he then advised we needed to get itemised billing to see who stole the sim card. I didn't received anything so decided to go into a branch. I went to Cresta, Clearwater and Sandton and all consultants could not assist as the account was locked. I called in numerous times and all agents said they could not assist me and would transfer me to customer service. I waited hours on the phone and no one ever answered. I sent 2 emails via the website with no response. Every month my acc gets debited with over R8k and I have to go into a branch to reverse it. I got a call last month from a lady advising me that my acc was in arrears, I told her the sim card was ****** and I needed someone to assist me. She said someone would call back and they never did. Today I got debited an amount of R2933.60 three times, totalling an amount of R8800 for calls I never made. Quick to take my money but no help when **** goes wrong