I abandoned Fi after a trip to western Europe, where I was billed for 6 GB of usage in a single day on one of my data-only SIM cards, despite that the device the SIM was installed in (a 4G hotspot) registered only 200MB of usage that day. Support was completely unhelpful, and after escalation reported back that the Fi team has zero visibility into chargebacks from their carrier partners and ergo could not diagnose th…
Cellular service is much cheaper in Europe than in the US, so you might as well take advantage of it. International calling plans for American phones are horrendously overpriced.
Of course, the downside is that I couldn't call or text anyone in the States, but who cares? That's what apps are for. I was able to talk to and message friends/family in the US using Facebook messenger and LINE. While on my hotel's free WiFi, my VoIP calls cost me nothing.