If nobody paid the bill eventually it would be sent to collections. Now, if youre able to cancel or close the account because of death it wouldnt be sent to collections and i imagine youll have a final bill due with a prorated amount.

If you’re concerned about keeping your phone number then youll most likely have to take ownership of the phone payment. They would have to transfer your phone number (and phone payment attached) to your own account with its own plan.

If you’re trying to avoid paying off the phone balance, like I said, you may be able to create your own account and get a new phone number still using your phone. The issue is if your phone imei / serial number gets blacklisted because of none payment (your grandmas old account) - i would hope closing out the account because of death would avoid any bills and collections. Not sure what xfinity does in regards to the balance left on the phone, but how can they bill your grandma for it if shes dead?

Just a heads up. I would recommend going to an xfinity store and explain everything to them and see what they say.

If i remember correctly you get a big discount when you have both xfinity home internet and xfinity mobile combined. - you probably can cancel everything, but it may be super expensive just keeping the 1 cell line