Alleged unpaid account

During lockdown in 2020, I was unable to go into the store to pay my monthly instalment on my Foschini account. So i did an eft transfer as i had done for many years, prior to paying instore. For some reason, the 3 payments of R610 each were not credited to my account. Instead of contacting me to inform me, my account was handed over to debt collectors. As you are aware they send messages, emails and they telephone the alleged defaulter. iI have sent proof of all the payments that I made to TFG, and according to my calculations, based on the statements i received at he onset of lockown, i have settled my account in full. i have been in email contact with various employees in the accounts department and the only response I get is to request that i submit proof of payments made, which i have done at least 4 times. i have blocked the phone numbers used by the debt collectors to contact me, because there could be as many as 20 a day. i still get messages informing me that my account is in arrears and that i should make immediate payments. how do i get them off my back and get acknowledgement that my debt has been discharged? regards Caroline