Best way to make phone untrackable?

I bought a prepaid phone in cash. It was activated using a public wifi, and has been turned off since then. My current plan is to keep it off when not in use, as to not have cell towers keeping a log of my movements.

Whats the best way to avoid pinging cell towers when I turn it on? I needed to get a prepaid plan to activate the phone and receive a phone number. But if theres any tricks …

cash current log phone privacy public public wifi wifi