Incorrect Debit Amount

Terrible service from Cell C after they deducted extra money from my bank account because of their inability to allocate payments correctly. Their assistants I talked with cannot make sense of payments even when they have my statement open in front of them and argue against the facts and proof of payments reflecting on the statement. Their service is beyond terrible, and I will definitely not be renewing my contract. I've been a Cell C customer for around 20 years now, but it is definitely coming to an end because of this debit issue.