Apple Music subscription through Verizon is not working stating subscription being used by another Apple ID

Hi there Grace_victory,

Thanks for joining us in Apple Support Communities. We understand you're unable to redeem an offer for Apple Music through your Verizon account. We're glad you're here, and we'll point you in the right direction.

"If your offer isn't listed, it might have come from another company. Contact that company for help with redeeming the offer." Have a look at this link to learn more:

If you can't redeem your promotion for an Apple subscription

With that said, you'll want to reach out to Verizon for more help.

Take care.