You can cancel the wrong DD by requesting your bank to stop it. I think you should do this but make sure SP know what you are doing and that you want to set up a new DD linked to your real account. If they think you are just stopping payments for no reason it could damage your credit status. Glad you have made some progress with your two meters.
Nobody answers the phone, It is pathetic that a copy of their size doesn't have enough people in the call centre. Their service is absolutely rubbish and they have messed up several accounts and failed to terminate them. I can't even talk to someone to try and get fixed. Are there any other numbers to call?