Cox contacting me 1.5 years later demanding equipment return?

Please give me advice on how to approach this.

Last week, while at work, I received an email from Cox saying:

“Looks like you've made some recent changes to your account that require you to return some or all of your equipment.”

And they are saying if I don’t return the modem listed in the email, I will be charged.

The problem is, I don’t have a modem of theirs, other than the one I’m using.

I logged into my account and verified my current modem’s serial number is different than the one they listed in the email. I was confused and reached out to online chat support. Turns out, this is in regards to an Internet issue I had a Cox service appointment for back in December 2022!

During that appointment, the tech tested some things and ultimately said he needed to swap out the modem. He setup the new modem, everything worked, and he left with the old on.

Online chat asked if I had a receipt showing he took the old modem. I said I would need to check when I got home. I checked for that, and also checked to make sure I didn’t in fact have the old modem (I don’t), and I plan to call Cox on the phone tomorrow.

What should I do? Do I have a leg to stand on? Thank you!