Telkom Demanding Money that I don't even have

I have taken a cellphone contract with Telkom mobile SA and I have had some financial difficulties in the past 4 months and haven't been able to pay my monthly installments. In October 2018 I have managed to pay all that was due for the months that I have not been able to pay even though did I not receive the data. I contacted Telkom to inform them that I have paid and would like my sim cards to be unblocked only to be told that they cannot unblock my sim cards because they have decided to cancel the contract and they are going to debit the remaining amount for the contract in cash by the end of November 2018, mind you this amount that they are saying they will debit is almost all of my salary. Telkom never contacted me to make me aware that they were cancelling my contract, they just did and now they are demanding this ridiculous amount of money from me. Please assist somebody.