I have a credit card with ~£5,000 balance and the interest rate is 27% APR.
A few months ago I was checked my transactions online, looking for the latest interest charge, but I couldn't find it. So I called them and the rep said that they couldn't find any interest charge for the previous month, nor the last several months. I joking said something like "long may it continue" and we end the call in a friendly and courteous manner. So I expecting a large interest charge the next month, but again there was none.
I have been using it quite regularly, and paying 10% of the balance every month (as I have for the last few years).
Shall I inform them that they still haven't charged me any interest ? It's been 6 month now since the last charge.