if your bank refuse they breaking the law
The bank can attempt to request a refund, but it is possible for the other side to dispute this. There's a very good reason why only certain reputable companies can use the direct debit system.
When notified, the bank debits their dd-suspense account and credits the customers account. They then send off a direct debit indemnity claim form to the other company... and wait. Once a week someone in the bank balances the dd-suspense ledger.. so in other words check to make sure all refunds are received. If the other company hasnt returned it after a month, then the bank has to chase.. and it is possible for the company to dispute. In cases like this, the bank has no alternative but to re-debit the customers account.
That is why the dd guarantee should only be used if a payment has been made in error. Believe me Ive dealt with 100/1000s of these over the years and it does sometimes come to stale-mate.
The other option we used to see is that the company would refund the bank, then simply chase the customer via other means. Whats one of the first thing BT are going to do if they feel you havent paid a bill?
I think notaclue would be far better taking this up with BT direct and hope that he can get someone to see sense. This is where I'd be complaining to.. Id perhaps even go to the top if need be.
Yes if you are stuggling you can buy some time by using the ddguarantee, but in the long term its not always the best option. You'd need to investigate other options such as the ADR or OFCOM.