Last year I missed an emergency call from a friend, that I was partially expecting. The call was from their caretaker's phone and I didn't have the number in my contacts, so I ignored it. They didn't die that time but they could have, and I wouldn't have been there.

Ignoring calls is simply not an appropriate solution to this. There are no appropriate individual solutions to any systemic problem, including this one.

Oh and in the United States at least, most government agencies will contact you by postal mail if you owe them payment and none of them accept gift cards or bitcoin.