Product: Payday loan, title loan, personal loan, or advance loan

In late XXXX I obtained a check for XXXX from XXXX XXXX to payoff my Upgrade personal loan. 
I called and talked to a customer service rep from Upgrade who told me where to mail the check and what info needed to be included with check. I had let her know I was paying off the loan and closing the account. I had asked specifically for everything that needed to happen to pay off the loan with the check. 
I mailed the check with tracking information and Upgrade received the payoff on XX/XX/2023. Tracking information confirms this. I was told 'processing ' can take 10-14 days but I would be credited with the check arriving on the XXXX. ( Upgrade strongly tries to discourage paying by check but this was the only option through XXXX XXXX company. 
I made several attempts to look into why my payment was not being credited to my account and it not being in paid off status. I sent numerous emails and was told that they could not look into it for 3 weeks. I made several attempts at phone calls. I would be on hold and it would play a message saying wait time was 17 minutes ... ..then I was on hold for 45, 60, 85 minutes with no one EVER answering the only Customer Service phone number. Email wasn't much better, but I eventually was able to escalate the issues and get a response, after it had almost been a month AFTER Upgrade received the on time payoff check. XXXX XXXX can verify all of this and the issues Upgrade has given both myself and the Title company during this payoff process. 
After a month, Upgrade stated that the check had been rejected because it did not have to proper information. Which was blatantly false as I included all the information Upgrade had stated I needed to include, when I mailed the check. They had previously tried to state they never received the check but my tracking information made that impossible, as it clearly shows it delivered on XX/XX/XXXX. They never in all my attempts to resolve why my account wasn't being updated as paid, told me once that the check had been rejected. I was never informed until a month later. They said they mailed it back but I also never received it. 
So, a month into this payoff process, I get XXXX XXXX involved, as they have to cancel the missing rejected check and reissue another check. I get ALL the information from Upgrade a second time, and try to get a non- XXXX XXXX XXXX to overnight the check directly from the Title Company, but " Upgrade no longer has that option '' according to Upgrade Customer service rep, who I had to get to call me via email to actually speak to someone from Upgrade. So, XXXX XXXX mails a second check to Upgrade WITH a current statement from the account and the information that Upgrade wants with the check AGAIN. This was XX/XX/XXXX. It has been almost another month and Upgrade is still not crediting my account as paid. I will be speaking with someone tomorrow, who I insisted call me, to try and have them locate the payment and credit my account. I have contacted XXXX XXXX about getting me the information I will need from second check tomorrow. Essentially, Upgrade either is trying to draw out the process and charge fees and interest in refusing to allow me to pay off this account, or trying to not allow a check payment as payoff. Either way they are literally refusing to allow me to pay off this loan. I have done everything Upgrade told me to do in XXXX for the payoff. I sent a prompt payoff check that arrived XX/XX/2023 with all of the information Upgrade requested. It was on time payment as well. Now Upgrade is trying to say I am XXXXXXXX XXXX  behind in payments when they either lost, or rejected, the original payoff from XXXX and quite possible lost the second check as well. This is predatory loan behavior refusing to allow a patron to pay off their loan in full. Making the process unnecessarily complicated, difficult, or impossible to complete. Trying to rack up additional interest or fees while Upgrade is the sole cause for the 'delay ' in payoff. I did EVERYTHING they stated I needed to. There is NO reason the first check shouldn't have been credited to my account to pay off the loan. 
There is definitely NO reason that they should have lost or rejected a second check to payoff the loan. 
I want to bring forward any and every legal and other investigation into this and make sure no one ever uses Upgrade and has to deal with this again.