Here is my experience, YMMV.
If you are in the US, they will sell you a prepaid plan. No problem.
Notice, Tello does NOT provide international roaming service. I have Tello and Tello confirms this on their website here:
Tello: Do you offer roaming?
"
Canada & Mexico
Tello does not have a network in Canada or Mexico and so we do not offer full service in either of those 2 countries and there is no roaming available."︀
They claim Wi-Fi calling & Text, but in reality, it's only Wi-Fi calling. Not Wi-Fi︁ receiving There is no room in the app for even a text.
I've had Tello︂ for +2 years. When I fly into the US it works fine. It doesn't work︃ in Canada or Mexico for Wi-Fi call receiving or Texting (sending or receiving). You can︄ call another phone via Wi-Fi though, but for this I use Skype.
It doesn't work︅ in Europe, and it doesn't work in Argentina, Brazil, Paraguay, etc, either.
I am in︆ their forum community and some "people" claim it works despite Tello's own disclaimer, but I︇ suspect "oversight" on their part.
You can try it and let us know, but if︈ someone was holding a g** to my head for the truth, I would say it︉ doesn't work without any hesitation.
Good luck!
Most banks nowadays will tell you:
My system is saying this is not a︋ compatible phone number.
The bank operator doesn't even know why.