I take advantage of credit card companies all the time. My favorite thing to do is this:
You know when you are at a department store and they offer you a massive discount on your purchase if you get their card? If I am already there making a massive purchase (I have a large family) ... I get the card, receive the deal, then simply reach into my pocket and pay the bill with the case I was going to use, then cancel the card.
...
After about 6 months or so (about as long between large purchases) you can do the whole thing again.
lol
I’ve done that. Mostly at stores I seldom shop at. They’ll sign you up for the card right at the register, get the discount, pay off the balance and cancel the card.