Vodacom debits after contract ended

A previous contract that ended in July 2021 was not renewed with Vodacom. Every month for the last 5 months I have had to dispute the payments to my inconvenience with FNB either in the bank or on the app. The amounts are as follows October R672.86, November R958.85, December R1245.84, January R1237.85 and February R1237.85. The contract was taken on my moms name when I was in campus and since then she has called them every month for the last 5 months to enquire. I have also stopped the debit with FNB but for whatever reason the references change and I still get debited. Rectify this issue immediately as this is extremely frustrating and inconvenient.