APPALLINGLY BAD SERVICE - ACTUALLY NON-EXISTENT SERVICE

My account number is SOO1541, I cancelled the fibre with Supersonic in June 2002 as we moved house. They are so bad that, even though they refunded for 2 months and I had to return the November debit order, they are still persisting in charging me after numerous emails asking them to stop. It is apparently impossible for them to cancel their invoicing and debit order - and my bank tells me thre's nothing they can do - only Supersonic can cancel the debit order. PLEASE ... if anyone in Supersonic reads this ...... HELP ME!!