MTN overcharges me on contrat

If I could give them a 0 star rating I would. MTN is a dissapointment. They offered me a data contract and they have been overcharging me every month. I raised this query with them and they kept overcharging me. I had to reverse their debit order and only now they are escalating the query to the billing department but they suspended my services. I now have to wait for their process and they dont want to give me access to the department that can help me, the only thing they do is to tell me to wait. When they take my money every month they don't wait and now they owe me and wont even give me the services as per the contract agreement. This is **************** because by the time they will reactivate my services i would have lost out on services. Furthermore I cannot even cancel this contract with them.