Wife returned router last year with some other equipment, they didn't record it. They also accidentally terminated our acc 😂 will they settle the $90?

TLDR: in addition to the constant errors from our local Spectrum, they didn't check our router in last year. So after they ACCIDENTALLY terminated our account and made us create a new line of service, they think we owe $90 for a router we already returned last year on our previous line of service. Will they just send the $90 to collections and settle for less? Will they clear it as a courtesy? According to UPS this happens frequently

Last year we switched to our own mesh setup and didn't need the router anymore. Spectrum had also sent us some new equipment when we changed our package, but we decided to keep the original modem so returned the new package of equipment and the old router we no longer needed.

This year, our local Spectrum accidentally cut our apartment's service and ended our account because someone at the store either made a typo or didn't check the new customer's lease. They tried to lie their way out of it by putting fault on the customer for giving them the wrong apartment number, but didn't realize it was still on them, because they had been swearing that they checked this customers lease and it had our apartment number 😂

Anyways, their solution was that we open a new account to fix the issue, and they assigned us new equipment. I returned the modem from the previous account to the UPS store but started getting emails about the router returned last year. Wife doesn't have a receipt (year passed, didn't scan whatever receipt may have been given) and apparently Spectrum/UPS doesn't keep records in the system. Before I learned this, the UPS rep had even told me that Spectrum tends to still come after customers even though they returned the equipment, so told me to save my receipt for the modem because no record will be stored in computer.

Tried reasoning with the rep at Spectrum store but she basically said my wife is lying to me and advised we either find the imaginary router or pay the $90. Super unprofessional btw, almost impulsively ended my service right there out of spite. I know it's just my local store and not Spectrum as a whole so figured I'd try to figure it out first.

Will they end up settling for less if it goes to collections? Is my only choice to eat the $90?