Why Telkom does my pensioner mom still receive bills after service was cancelled?

My 77 year old mother decided after more than 30 years to cancel her Telkom account. She went to Telkom store at Langeberg Mall 6/6/24 and was helped. She paid R659.95 to close account on account number *** - service number ***. Now she received a new invoice for the amount of R928.11. we have been warned that Telkom do this. Please, sort out your systems and deal with your pensioners accordingly and with respect. She did and pay what she was supposed to pay according to your systems. Please contact me (her son) to discuss urgently. ***