Negative Credit Paypal

I am in negative credit for 85.00$ on my moms paypal (I'm not sure where the other 10 dollars came from)

I can't close my account with negative credit on it.

I sold a runescape account for 75.00$ and never scammed it back, and 2-3 months later he claims an unauthorized transaction.

Now I know it was him unless he stole the paypal, which i'm basically 100% positive he didn't but he can always claim someone stole it from him.

What should I do to remove the negative credit, I'm not paying them back because I don't beleive its my freaking fault.

I have like 4 questions and here they are

1.) If I never pay them back what will happen?

2.) Can they take money out of my bank even if they want to?

3.) Will calling them even help me in any way?

4.) Will changing my name and bank number work?

 

1. If you're registered with real info, they will email you and call you many times after a few months
2. Yes
3. If you're planning on paying it back eventually, you could probably delay them from harassing you if you phone them
4. I doubt it