Cannot update banking details and not allowed to cancel account

I have updated my banking details on Home-Connect's online portal last week. I have now received a sms that the debit order wasn't submitted because of "incorrect" banking details. The banking details however are 100% as per bank account opening confirmation letter.

To make matters worse, since my banking details doesn't work, I wanted to cancel my account by giving 30 days notice. Now I am told that this is not possible even though today is the first working day of the month.

Stay away from Home-Connect!!