Charged interest after I paid in full

The 0% interest on my card was at an end and I'd intended to pay it off in full to avoid interest but when I got round to checking I only had two days until the due date. I gave them a call to change the DD but they said it was too late to do this but I could go into the branch and pay.

So I drove up to town and handed over a couple of thousand in cash which was the exact amount to clear the balance. I've just got my statement and they've still charged me interest. All my balance is made of now is the interest charge.

I called them and apparently I'd paid the money in too late and they referred me to the back of my statement which states I need to pay money in at the branch 4 working days before. Indeed it does but I was told that I wouldn't incur charges if I paid cash.

Have I got any chance of getting the interest charge removed or is the most I could expect 30p to cover my petrol costs for the bad advice?

IANAL or financial expert etc.

Was it a bank / building society credit card, and the payment was made at the same bank / building society that issued the card ?

Although you're probably on a hiding to nothing, you've lost nothing by writing to complain that their inability to credit transactions within the same institution isn't your fault, and would only expect the 4 day limit to apply if paid in at a different bank.

A fly in the ointment I suspect you might hit is that many credit card accounts are offloaded onto a third party (such as MBNA) who run the card in someone elses' name. Even though the card may say (for instance) Alliance & Leicester, they don't run their own card, so effectively you are still paying into a third party account despite it being in "their" name, hence the 4 day delay for it to be credited.