Bad service from Telkom

Hi I had an SIM card data account with Telkom my account ended last year October 2023.But before my account finished I cancelled my Telkom data SIM card,I got an SMS saying my account is cancelled but when n went to my bank to check for credit they told me Telkom put my name as a bad payer on my Experian account then I went to Telkom in N1 city just to find out what was going on then they told me my data SIM card was cancelled last month but I told them my contract ended last year october.I am very upset with Telkom it was there mistake now I am being punished.I can't get credit because of them 😡😡😡😡🤬🤬🤬🤬🤬🤬