Poor Telkom Service - unauthorised debit orders and lack of accounting - Telkom breach of contract

We entered into a contract with Telkom in January 2018 of R449/month. When we received our home router 3rd week of January, and contacted Telkom to confirm the debit amount for end Jan, we were informed to wait for the first statement, and that the 1st payment will only take place end Feb. They confirmed that the pro-rata amount of R320 along with the subscription of R449 will be debited end Feb. End of Feb, they only debited the R449. We enquired again, and they stated that we will have to make payment of R320 ourselves, which was done on 11 March. Statement received 01 Marc h still reflected the R320, but we ignored it, as we already paid. The statement dated 01 March stated that the debit amount of R449 will be debited on 03 April. The debit order did not go off. However the account was debited with R898 on 13 April - this being double the contractual amount. I have had mail correspondence with Telkom, enquiring why, and they stated that we have not paid our ac count. How is this possible, if it goes off via debit order. I have now been debited double the amount, R449 of which is only due to be debited end of April. How can they double deduct without consultation. Does this not constitute breach of contract on their end, as they debited on a date not agreed to on contract. When I informed them that they must listen to all the recorded calls made already, they don't answer me. I have double paid, yet they are still gong to debit end of the month? I need help getting this resolved, as they are not getting back to me. When you phone, you are kept on line to wait for 20 minutes. I want to cancel this contract, as they have breached it.