Avant review: Avant credit card

I mailed a payoff for my credit card statement balance. The check pay to was to AVANT. and I provided them with the check numner. I found out that the comapny cashed the check on December 3rd but has not applied ti to my account and it is now December 12th! The check was made from my title company as part of refinance on my home and checks were mailed to all my creditors for payoff. Avant is the only one who seems to have a problem with this. This should be MORE than enough information for the company to find a check THEY CASHED! and find out where the money is!
Why is the company cashing the check without applying it to an account? I am overly frustrated!
I Mailed the check to the address on your website.
Avant, LLC
PO Box 9183380
Chicago, IL, [protected].

I have made several calls and spoke with a few supervisors. Their customer service is terrible all they do is tell me what I can see in the portal. I don’t even know why they are paid to convey information that I can see on my account. Even the supervisors are zero help. They ask the same questions. At one point an agent told me to ask my title company to send them their bank statement to show the check as been cashed?! This issue has been escalated twice now and I have not received any calls from a manager NOR do I have any reference of it being handled! I am very worried that they mishandled my check and applied it to something they should not have! No one is giving me any answers! This is so mishandled!