Incorrect billing

I have a debit order with Wesbank and have recently submitted change of banking details of which wesbank has sent me an Email confirmation that they have received the document and will be in place for the next debit order and that I should make an EFT for that mnth as it takes time for the new information to be active.I have not been debited as arranged and now they handed the account for collection.they also don't return phone calls as the manager was supposed to call me back.