Pay the bill, or risk being sued in Civil Court (and having your credit rating ruined).
If they did not give you a Trespass/Ban notice, you should be able to shop at Walmart/Sams. I would call the store LP and ask first - if they did ban you, you could be arrested for Criminal Trespass if you enter ANY WalMart.
Since they called police, you can also expect a court date.
All in all...expect $2000 in fines, fees, Civil Demand....You may also want to retain a lawyer or ask for a public defender.

