A very useful posting Wolfman- thank you.
I spent 20 minutes trying to get a reply after holding on with Natwest card center on 0870 3339091 after which I realized I was paying up to 6p per min.
This was after they sent me 4 blank credit card cheques and an invitation to transfer balances, and I wanted to tell them to stop sending me this unsolicited mail.
I did not get an answer and gave up, then I remembered your posting and found a freephone number 0800444252
this was answered almost immediately and the bussiness done- I hope!