Without reading your contract or all of the details of your subsequent agreement, I cannot tell you the specifics of your rights.
However, what I can infer from what you have posted, is that this business is likely violating multiple OK statutes with regards ***** ***** the business and professions code, and related acts.
The easiest (and least expensive) mechanism for you to deal with this is to simply file a complaint with the Oklahoma Attorney General's Office (this kind of conduct needs to be addressed by the state's law enforcement officers, they can take administrative and/or criminal enforcement action against businesses that do this kind of thing).
You can file a complaint quickly and easily here: https://www.oag.ok.gov/oagweb.nsf/ccomp.html
To deal with the business, it is probably easiest to do so in writing - send them a letter reminding them of both the series of events that led up to the repossession, and the terms of your agreement (you have 30 days to repay).
You can also include in it details of the subsequent phone call(s) where they made additional demands on you.
(This is called a "confirmation letter" - but it helps to document your side of the story/contract and can protect you).