If it is a worst case scenario where you have to spend some money, the cheapest way is probably to buy a Tracfone (here’s one for $15) and use it in WiFi mode. Probably not an ideal solution from your POV, but if it is that or nothing…
You’ll have to buy a “plan”, but that can be a one month $10 card that you never need to bother refilling if you use WiFi.