I remember I had a childhood best friend and one day, as a child, I dialed up his grandma’s phone number because we were young and did not yet have phones. It said the phone number was no longer in service. Someone told me this means that the owner of the number has died. Is that likely??
In this scenario and considering old people are at a higher statistical risk of passing away: it is possible. However, the same message will play if you end your subscription because you moved to a different place and couldn’t transfer the number to your new place. Disused phone numbers don’t get redistributed right away, the phone companies use their own system of how long it has to remain fallow.
A phone number can go out of service for any variety of reasons
It was the message for when the phone service was disconnected. While this often happens after the person dies, it could have also meant they were away for an extended time. (Such as "I’m going to stay with my daughter for a few weeks after the birth of my grandchild.)
Absent other explanations, though, death is a probable explanation.for a grandmother’s phone being disconnected.
(Note that “poor with no money” is also possible, since phones cost money.)