Incorrect Billing

I opened an account with telkom in November 2019 for a home landline. I did this at the Telkom office in Main Street Johannesburg. They explained to me the package that i am taking is R299 pm which includes the line rental, free calls to telkom numbers, 100mins to other networks and 5GIG data a month. I was contacted 5 months later and Telkom said that i owe them over R6000 and i should pay up or my services will be suspended. I logged an account dispute becasue we never used the phone often and never went above the free call and mins. When telom got back to me 3 weeks later they said i owe them R2000 for the line rental because they never billed me and i owe them R4000 for data i used. ( and by the way they said i used the R4000 data over Jan and Feb. ) , i agreed to the R2000 line rental but the data, i asked them how can a person use R2000 data in one month. ( by the way i have my own router that we use data from ), the only explanation they could give me is that the data came from the settings from the phone, what the hell does that even mean, whos problem is the phones settings. when i took out this account i was given a hand set and told when i get home plug it in and its ready for use. my billing will go according to my package. I have spoken to many other people about this and many say that Telkom has a billing issue. I still await feedback to this day about my account as my balance is still on over R6000. I want to settle what i owe for the line rental ... but the data ... really Telkom R4000 data in two months are you insane ??????????