New phone number tied to someone else’s account

I got a new phone number for myself recently. After updating all my accounts with the new number, I began getting xFinity text alerts from someone else’s account sent to my phone - I assume whoever had the phone number before I did. Is there any way for me to have my number taken off of their accounts to ensure they’re separated? Whoever the old owner of the phone number is seems to not like paying their bill, as they received a notification that service was deactivated due to lack of payment, and my service appears to still be active and I know for a fact my payment cleared.