Did not change my bank details. Debit order failed on Gap cover.

Last year, I called and emailed numerous times that my bank details have changed. I filled in the change of details form. I called and emailed to follow up. Was told I would get a call back last year. I'm still waiting. Nobody rep**** to my emails. And now my debit order on my policy failed because you are still deducting off the wrong account. Why can't you serve your customers properly? This is my second complaint against you. It's getting tiring now.