I only have two phones right now.
One for everyday calls and purchasing, the other for when I don’t wish to leave a lit up map of when/where I’ve been traveling to. The second phone, I take the battery out, when I’m done with it. Noting that important. Just old customs of insuring my privacy when it matters.
Yes. I have a’throw away’ phone too. Most services online are now asking for a # ... I have no idea why I guess for security due to bots etc. but a lot of people are NOT comfortable with giving their number out online and it tends to irk them.