It's a big problem and another way banks are forcing people into credit. I remember doing the same thing as a kid of around 19. I got a credit card and used it to establish that I could pay credit. Before long the $2K limit was $10K and more. That's how they trap people. The fuckers didn't trap me though, I learned quickly. Many do not.
I can tell you're butter about it and justifiably so. We, (the general population) are treated in this way and worse and all we can mostly do is suck it.
When you go back, might I suggest Mars Bars and Toblerone and when you get light globes, consider LED ones.
RE: Interest irresponsibility