Capital One blocked ym credit card the other day for forgetting to pay them 26p.
I cleared the full balance, nearly two months ago miss-keyed the pence part of the payment on my Internet banking and ended up owning just 26p to them. Never missed a payment in the 2 years I've been with them and always paid in full but they still blocked my card and tried to charge me interest. Strangely it wasn't on the 26p (x% of 26p is £0 in anyone's book) but on the items I'd bought since I missed the payment to them.
Suffice to say they refunded the interest and unblocked my card. Assholes.