Telkom changed contract without permission and billing excessive amounts

I opened a fibre contract in April last year for R1311-00. Since April 2018 my account has had additional charges each month which I have queried on a monthly basis. The excuses from Telkom are different each time. Today I received an sms from lawyers saying Telkom has handed me over even though I have been paying the R1311 each month according to my contract. I went to the Woodlands store today and the manager - Zoliswa Nqayi - said she can’t help because it’s ‘knock off’ time. Other staff got Billing to phone me and they said it’s Sales fault and I must phone Sales. Sales says it’s Billing’s fault. So what do I do? Nobody wants to take responsibility and the lawyers are on my back. The only thing I learnt from today is that my contract is NOT the initial contract I has signed up for and Telkom is billing me like crazy!