Bad Service on the billing

I really don't get it how such a big company can struggle with a simple thing like debit order. Telkom stopped debit my account and in December 2020 and January 2021 they started to debit on a different day. They I went to the branch to report this and to ask them to stick with debit order given to them. February they didn't debit at all. A call to a billing department was logged, then I paid manually. Then I started receiving calls from different collection company, I would tell them I have asked Telkom to debit my account, this went on several months. Ended up have to pay by EFT. But, every day I received a call. I would tell them I have paid but I still received call to make payment. Their service is really appalling. The service standard has dropped drastically.