Price Watch/Conor Pope: There's no question that credit cards are convenient, but they can be very costly.

Using them to withdraw money from an ATM is one of the worst ways to run your finances: as well as levying interest on it immediately (unless your card is with Bank of Ireland or AIB), your credit-card company will probably charge you the greater of about €2.50 or 1.5 per cent of the transaction.

There is a way round the charges, however: if you keep your card in credit you should avoid any fees for withdrawing cash.

It pays to keep any eye on your account, though: Ronan Barry got in touch to complain about the way Bank of Ireland Credit Card Services handled his account and to advise other readers to be alert.

He withdrew €100 from an ATM with his credit card when his account was considerably more in credit than that. "When the transaction hit my account a day later there was a €2.54 transaction charge on it," he says. After a quick phone call the bank agreed to refund it.

Shortly afterwards he withdrew another €700. Barry says: "€600 was my own and about €100 was the bank's. . . . I was charged €10.50 for this transaction. When I spoke to their customer-services desk they told me I was being charged for the whole withdrawal - effectively, paying 1.5 per cent to withdraw €600 of my money or paying over 10 per cent to take out €100 of the bank's money.

"If I had made two withdrawals from the ATM, one for €600 and another for €100, I would have only paid €2.54 in total. The bank was totally unwilling to refund any of the charge.

"While on any given occasion it is not a huge amount of money per individual, it is another example of these people blatantly, arrogantly and systematically ripping off their customers," he says.

Not so, says Bank of Ireland. The company's credit-card arm accepts that Barry should not have been charged the €2.54 for his first transaction and that he was right to complain.

"We don't charge cash-advance fees when you're using your own money," says a spokesman (although he cannot explain how the wrongly applied charge had been triggered).

As for the €700 withdrawal, he says, the €10.50 charge is in line with the bank's clearly stated policy.

"You will not be charged a cash-advance fee if your account is in credit or has a zero balance after the transaction has been concluded."

As Barry's account was €100 in debit when the transaction ended he was charged the standard 1.5 per cent of the withdrawal.

"We try to make our rules as transparent as possible," adds the spokesman.