I work in retail and 99% of these are a pain! Many have special keying instructions, or split tender instructions, and it is difficult to keep up with all the companies issuing them these days. Like someone else said, some also take a fee off monthly if there is a balance over a certain time limit. I've seen some that take a fee off for every balance inquiry, and for every swipe at a store. I had one customer last year screaming at me because she thought she has $25 on the card (that was the issuing amount). I swiped, it was declined. She insisted I swipe again, it was declined. I suggested she call for her balance, and when she did it was only $20 - they deducted $2.50 each time I swiped it in the store. What she didn't know was that they were about to charge her $2.50 for the balance inquiry call, so when I went to swipe her card for $20, it technically was now down to $17.50, and it was declined. Take off another $2.50 for swiping...this went round & round until she almost had nothing left on the card!