Yes, check them!

I was overcharged $674 last month. I had a contractor out to my house and initially, I gave them a CC# to activate my account. Then when they did the install, I paid with another card. Sure enough, they charged BOTH cards! It happened 2 months ago for $280.xx with a furniture store, too. Imagine what they'd get away with if I didn't check!

One time, my mom went to a little mom and pop restaurant and paid about $24 for her meal. The charge never showed up on that month's bill or the next months bill.... about 4 MONTHS later, the charge showed up, but for $40 more! Luckily, she keeps reciepts and itemizes EVERY bill.