The first thing was to get a tv, my simple plan was to pay it off, get some credit score, and then use it again. Next was some big emergency expenses, that raised me to I think $900 debt. Bad, but not horrible. Then my dumb young 20 something ass decided I was a genius by setting up a fake business to get a card reader and "purchase" money to myself to pay rent. That's what really got me to $2000 and stuck in debt.
Then I think after hovering around that and making payments I got this message in the mail like 2 years later saying I got a rate limit increase to $4k, i think it was the finally having some breathing room mixed with emergency purchases and dumb shit that got me to 4k, honestly i don't even remember so it must have not been important.
Now that I'm a little bit less of a dumbass I've worked my way down to around $3,500, which is hard because the more debt you have, the more fees you pay each month ( I think at 2k I was paying $90 interest a month, and now it's like $170) because go fuck yourself, but I'm whittling away at it. I can't wait till I'm finally down to zero and I don't have this monster looming over me anymore, fuck credit cards.
And to answer your question if you don't pay, eventually they'll sell your debt off to loan sharks who will harass you until either you pay or they throw you in debtors prison i think