Impossible to cancel a expired contract

My mom had a data sim where the 2 year contract ran out on an she did not renew it because the signal in Bela Bela sucks. (She installed fibre) The contract ended in 2022 - She tried calling cancellations but no luck and eventually gave up, Because the contract in any case ended. She recently received a few SMS's (Received them because she is on MTN) saying she has been handed over to the creditors due to her being in arrears on her Vodacom account. I recently tried to assist her in finding out what is going. I called 082 135(3rd time lucky) and explained the story and was told to speak to cancellations, the lady put me through to the cancellations department and before anyone answered line went dead. I tried the 4th time calling 082 135 and got through on the first try, explaining the same story again I was put through to accounts. The accounts person told me my mom was owing +-R 500 on the account. I was told to call cancellations ***. I tried calling the number for 2 days without any luck, there is no option to speak to anyone, the data sim number is not accepted by the automated system and the number I'm calling from is not Vodacom number. My mom went to a Vodacom shop today and paid R235 rand which the staff said was the only amount outstanding. She still received a SMS today on money outstanding.

My mom is almost 80 years old - She will never buy anything on credit again so blacklist her or whatever but we are done with Vodacom