I use Verizon. They have a service called Travel Pass, where you're charged $10 per 24-hour period, with unlimited talk & text. When I used it, they sent a text alert in advance of the next 24 hours starting, giving me a chance to go to "airplane mode" to avoid being dinged with a charge for the following 24-hour period.

When travelling internationally, I keep my phone on airplane mode with wifi calling activated, only using the service when I need it (starting Travel Pass by disabling airplane mode). I've used it in Germany, Netherlands, UK, and on the island (both sides).

To register, text Travel to 4004