Telkom data contract - a ****

I took a 10g + 10g Data Contract for R139.00pm with telkom around April 2021. Everything was well until December when suddenly R260. 62 was debited from my account instead of R139.00 as per contract. I queried the amount but was ignored. January I received a statement indicating that R513. 31 will be debited. I made follow-up but there were no answers. I then reversed the R260. 62 and come debit date R770 was debited.

I went to Wonder park branch for some explanation, I even tried to cancel the contract but no assistance. The billing department called and said they will investigate the matter and get back to me in 70hrs. It's now 5 days and I haven't heard anything from them. I called the billing department and they said calls were made from the data Sim hence the amounts but couldn't tell me how or which device was used because I only use the data Sim in my router and have never ever made calls, upgraded the card to make calls or anything like that.

Now I want to cancel the contract and I'm being sent from pillar to post. Since December I have not used the data Sim but already I've accumulated + R30. 00 debt on top of the R139. 00. I wonder how much will be debited this month....