Phone number being de-registered?

I was at the Nashville Green Hills Apple Store on April 18th to trade-in my iPhone XR to take advantage of the Verizon $800 trade-in offer. Worked with Mark while there.

****My phone number is now being *de-registered* on my new phone in a number of days due to Verizon not having received my phone by your store- PLEASE call to resolve this.

I have been trying to contact you and not understanding why this store is not responding to resolve this.

I no longer have my old phone as I gave it to Mark on April 18th to send to Verizon. Verizon has not received my old phone. Today is May 5th.