Here's the full story.
I've been using an AT&T MVNO for years (introduced by a friend) and I'm pretty happy with it (not naming it here so that the piece won't come off as a soft sell, and that I won't be easily identified). My carrier, however, doesn't offer any international service, so I'm completely left in the dark when traveling internationally. When I read the Google Fi announcement, it appeared that with my data usage pattern, Google Fi would only cost slightly more every month and would still work outside the U.S., and the $200 credit was attractive, so I ordered their SIM, which arrived a little more than a week ago. I was of course vaguely concerned about Google's historic reputation in the customer support department, but figured that maybe I would get lucky and never have to deal with them, or maybe Google Fi customer support would be okay. Boy am I wrong.
Fast forward to when I got the SIM in the mail, I activated the service on my iPhone (XS Max) and kicked off the number porting process. It smelled slightly off right off the bat, since although I selected "other" as my carrier, the Google Fi app insisted on porting my "AT&T" number. Porting failed a few hours later so I called Google Fi customer support. The customer support representative asked me about my carrier, and actually called my carrier to inquire about the porting process. He came back with the information that my carrier's porting department closes at 6pm EST, so he called me back the next day to restart the porting process. At that point I was actually pretty impressed with the customer support. (It was later revealed that I initially entered a wrong address, since I had moved and hadn't updated my address with my previous carrier. It was not clear if porting failed due to the wrong address, or because their automated system couldn't deal with my carrier to begin with. Anyway, since a human support agent was now involved, the initial error didn't matter anymore.) I was assured that porting would complete within 48 hours, and my case was closed.
It all went down hill from there. Two separate problems occurred.
First, although the number wasn't ported yet, I was actually able to use cellular data; the data usage meter started rolling, and I could see my data bill. Except one problem: although the connection showed up on my phone as LTE, the actual speed was around 15Kbps tops (according to fast.com). That's slower than typical 2G, and most websites, as well as apps that require an Internet connection, ranged from barely usable to completely broken. (It was actually an eye-opening first hand experience on how bloated the web has become. HN was still usable, and thank God a couple of sites I run still load with in 2 seconds. You don't need all the crap to be informative; who would have guessed.)
I called customer support again, and the rep (a very friendly guy) told me outright that he didn't have any support material on iOS (I didn't press him into admitting anything). He tried a bunch of Android troubleshooting instructions on me and they didn't work. Eventually we concluded that there was nothing we could do other than waiting for the number to be fully transferred and hoping the problem would automatically go away. A hypothesis that remained a hypothesis till the end.
The second problem was that the porting process stalled. Nothing happened after 48 hours, just a "porting delayed" status and "contact us". So I started calling them every day. Every time I was told that "a specialist is working on the case, I've left a message for them, and they will contact you by email soon; just watch your inbox." Except no email ever came, and I was never introduced to any "specialist". After another three fruitless days and being told the exact same thing, I asked the lady on the phone to ask the "specialist" to email me something, anything; I just needed to know that there was actually some human being who would give my case some attention once in a while. The lady promised to do that. Not surprisingly, again no email ever came. (Note: I'm not saying it must be Google Fi's fault that the porting process stalled; it could be my previous carrier. I don't know. What I do know is that I was promised communication from Google Fi, and I didn't receive it, despite daily calls.) So at this point I was pretty sure the "specialist working on my case" simply didn't exist. I would hope that passing their promised 48 hour threshold or calling them daily would elevate my case to some higher priority, but nope. My best guess is that they had a huge influx of customers due to the flashy marketing campaign, and didn't have the manpower to keep up. Nevertheless, I was not happy being (politely) lied to, or staying in the limbo state forever. Eventually, I called them again to cancel my service. I'm glad to report that at least there was no BS around canceling.
That's the whole story. YMMV.