Building credit after collections?

Hi, Redditors. My situation is kind of weird, so bear with me. When I was 17 (still a minor!) my dad put me on my own car insurance plan through Progressive. I gave him the money every month to pay it since I didn't have a checking account yet, but I never saw the bill. I realize that was a mistake now. Anyway, after a time, we cancelled the plan and soon after received a bill for around $700. I ignored it, because my dad said he would take care of it. Again, I know this was a mistake now. Progressive turned me over to a collections company, and I sent them a letter asking for proof of the debt - which they gave me. Now, I am stuck. I don't know what to do. I can't afford the bill or any of the payment plans they are offering. This bill has affected my credit score already and has prevented me from building new credit, as I can't get approved for a credit card with the debt collection still on my report. I don't know where to turn right now. I'm only 18, and I make nowhere near enough to have the money to pay this debt off in the ways they are offering. Can they even continue to come after me, when the debt was incurred when I was a minor? I do need to build my credit so I can get a car. Outside of this incident, I always pay my bills on time and am never negative in my bank account. Any advice would be helpful, sorry if this seems kind of scattered. Please let me know if there are questions I haven't answered.

TL;DR: debt incurred when I was a minor affecting my current credit score, not sure how to fix it

EDIT: I just checked my credit score online via NerdWallet and evidently the mark on my report is now a chargeoff. I have also emailed the company to try to explain to them that I was a minor at the time of the debt and see if that changes anything. I really just want the report removed from my credit score.