Pathetic at honouring their word

I have contacted DStv Multichoice for the past several months as firstly they weren't debuting my bank account and they kept suspending my service, so they reactivated my service promptly each time because they said there was a system error and that's why my bank account was not being debited. Eventually my bank account started being debited but by way too much and not the agreed upon monthly contractual fee. Every month they say I have a credit because they made a mistake and took too much but then the following month they over debit again. This is extremely frustrating as no one cares to help me. If the roles were reversed I'd be sitting with hefty debt collection fees. This is unacceptable and I think it's my turn to seek legal advise because I signed a binding contract with DStv and they are not sticking to their side of the deal. My recommendation would be find another source of entertainment or service provider because DStv doesn't know the meaning of customer service.