Worst service ever

I called to change my debit order as I have changed jobs. I was told to email my new contract and they would amend. Now they asking me for a payslip. I only start my new job 1 August, payslip is end of August so it is too late to amend. They so *********** and tell me I must call the call centre. how *********** can you be!!! Surely i have a right to choose a debit order date