Random Embarrassment

I was checking my credit card account the other day and noticed this random $18 charge. The description just said "Finance charge" and I didn't know what that meant, so I hurried myself over to the bank to check it out. I sat down with one of the bankers and explained the situation while she looked up my account. She then told me that the $18 charge was just the interest on my account. Now, when I hear the word "interest" I immediately become an optimist. Instead of thinking of the "negative" interest that comes with having a balance on your credit card, I think of having a savings account and any interest I should be accruing. So upon hearing said magical word, I did an immediate mental switch to the kind of interest I would earn, causing me to blurt out, "I PAY interest?!?" The banker gave me a very amused and condescending look that you might give to a small child who has just figured out that you have to untie your shoes before putting them on. I then went on to say, "You mean I'm not EARNING interest on this account??" She stared at me a little longer and then said "On your credit card?" which caused my mental synapses to instantly correct themselves and make me realize what I was saying. The best response I had at that point was, "Oh. Right." which I mumbled before walking my humiliated self back out the door.