Credit card debt and the subsequent interest fees are not something 23-year-old Lucy Metge loses sleep over.

Metge, a sales representative, has restricted herself to a $500 credit limit, which she supplements with a $2000 overdraft on her cheque account. Both are nearly always maxed out.

She usually makes the minimum repayment on her ASB Visa card, which accumulates 19.95 per cent interest on top of account fees. Metge paid off the card in full more than a year ago but she says the extra cost does not concern her.

"You pay for the service and the convenience. The most I pay in interest is about $10 a month. I know I'm throwing money away but it's manageable amounts."

Metge has more than $3000 in savings but chooses not to pay off her high-interest debt.

"I could pay off the lot and still have savings. But I don't pay that much in interest and fees. It sounds ridiculous but I like to organise it that way."

She admits she does not fully understand how her credit card fees operate. "When I first got one a few years ago, the bank talked only briefly about the interest rate. They were like, 'Hey, here's some money'." "

Metge's case is at the modest end of interest fees. One 24-year-old signed up for an ASB low-interest Mastercard and eventually took out a personal loan because she was unable to pay off the balance. She does not wish to be named because she works for a major bank but wants to warn others that credit card interest can be crippling.

"I got the card because I needed extra money to buy a car. I had no idea how the interest worked but the bank happily gave me a card without explaining it."

The then-18-year-old took a $1000 cash advance without realising she would pay 17.95 per cent interest from day one.

"I was paying the minimum each month, around $20. I was so young and dumb.

"When I got that credit card, I was earning $250 a week. I was way out of my depth."