Debit order date change

I requested a debit order date change for my savings policy via email on 16th September 2022 which was confirmed by Old Mutual to have been changed successfully. However, this was not done at all because my debit order went off on the date I requested them to change. I emailed and called but to no success. The agents will answer the phone and say hello and the line will drop. I call back and the same thing. None of the agents bother calling me back considering how long I need to wait on the line to so speak to someone. I am still waiting for a response to both my emails and numerous phone calls and have this resolved. Absolutely ridiculous service!