Poor service

I changed my banking account details on 22/08/2018, via the bank. Still Vodacom deducted my old account, as a result thereof my old bank is charging me for insufficient funds and Vodacom is also charging a fee for the debit order that was not successfully collected. I also called on 19/09/2018 in order to confirm if the debit order went through. I was told that it was successfully collected, however, this weekend I received messages that my account is in arrears. Then I called this morning and was told it is not Vodacoms' fault since there was no money in the account. Then I called the accounts department and after being transferred to wrong departments finally I was helped by a person by the name Gavin (I think), however, the call was cut (but somehow it went to the space where I had to rate the level of service received) and he didn't even bother to call back since I was trying to recap what he said when the phone got cut.