Very disappointed

I'm struggling for 2 weeks do do a simple thing of , changing my bank details after many phone calls to change bank details ,I was told to fill in a mandate form because bank detail had to be change from my account to my wife,we did send it through, discovery let us know they can't see clearly on the forms had to resend several times after a long struggle ,they came back today and said we need to fill in another form and resend ,bank details have still not been changed and everytime it's something new,so please phone me very urgently ,