Bad Telkom Service

I have been using the telkom mobile network for a few months with great regret. I am constantly having issues with them every month regarding payment. None of my other debit orders have issues. The debit order goes off then returned then I am hit with penalties that are not my fault. I have been in the store time and time again trying to get my account resolved. They are constantly taking off different amounts off my account sometimes even almost R1000 my contract is only about R400 odd a month. Every time I have gone into the telkom store to complain about it I just get told they will log it and get back to me which never happens. I also have to prove countless times that there was funds in the account. I have tried to call them on the customer care lines but nobody answers my calls no matter what number I call. Since I have been with the network I have had nothing but issues with my account. I cant wait for my contract to expire so I can take my business elsewhere. The service levels and incompetantcy of the staff are extremly frustrating. No account queries can be resolved in store . And the staff are also just uninterested in assisting with a solution. There is nothing good about the telkom network. This month again received a statement saying I was in arrears of R1600. This being after they took R900 odd off my account last month. I am getting tired of going into the store every month to get this sorted out with no assistance. I would like to know how I can cancel this contract without costing me a fortune as there is no service delivery. This is not what I signed up for when I signed the contract.