My question involves a consumer law issue in the State of: Utah

So basically we purchased a vehicle from a used car dealership that ended up having issues the first day of owning it. The dealership offered to trade it straight across for a Jeep they had.

We agreed and opted to buy a service contract for $1,000 and were told that we would need to put more money down to cover it, so we put an additional $500 down since that was all we had left. They then had us sign a piece of scratch paper with our credit card information to be charged at a later date for the remaining $500 (this paper had no additional terms).

After being told that we would get the Jeep for the same price as the other vehicle, noticed that $500 was added to the price of the Jeep, putting it at $12,500 instead of $11,999 as promised. I made the mistake of assuming that the additional $500 that was added was the remaining $500 owed on the service contract and signed the papers.

Nine months later we received a charge on our account for $600 and contacted our bank where they then conducted a fraudulent charge investigation and credited us back the money.

Around two months after that I received some court papers from the dealership saying it needed to be resolved in small claims. I then called to discuss the situation. I acknowledged that I should've been more thorough when signing the paperwork and that I thought they were dishonest for adding the $500 to the loan but would rather settle out of court. We agreed on a payment schedule and made the first payment of $100 where they then stated that they would drop the court charge.

Feeling like no effort was made to understand or make right the situation, I left a review detailing our negative experience.

Following the review, I received a call saying they will no longer accept the payments that we had previously made and agreed upon and will see us in court.

My question is this, on the actual contract of sale, it shows everything as being paid in full. So technically I don't owe anything right? I'm assuming this was done by the dealership to close the deal and get a check and was why they made us sign the promissory note. But because I signed the promissory note, will I still lose in court?

Technically and morally I don't owe anything since they added $500 to the verbally agreed upon price of Jeep. But legally do I? How will the Judge most likely see it?

Also can they go back on the payment agreement we made, even after payments were made, because of our review?

And my last question, can they add $100 as a "service fee" to the $500 from the promissory note that had no terms?

Thanks!