Okay, so for me I used to pay ATT for overseas service outside of the continental North America, originally about $50 per month, then $60, then $70, and now they don't even offer this Passport option, instead charging $10 per day (and from my experience they actually do charge that every day you have your phone connected to a network, that is, do not have airplane mode selected). That is highway robbery, so for Panama and South Africa, my two destinations over the past two years, I've gotten cheap local SIM cards with cheap data and just used WhatsApp for all communications, plus email. So, I don't have my usual phone number for simple phone calls or messaging (although here in SA I have a local number), instead I just buy data and everyone here and in Panama uses WhatsApp for messages and calls. Cost per month has been around $10, with reasonably intense data usage for navigation, messaging, photos and videos sent and received, some music, and news sources, plus of course lots of wind forecasts and KiteForum Spots etc. About 2Gb for each month here. Same for Panama.
An alternative you might want to check into is Google Fi, which last I checked is supposed to work on most phones now. It allows usage of the same phone and number worldwide. Friends who joined us in SA two years ago used it very successfully on their Samsung phones, and it is their network back home in the USA too. And lots of globe-wandering yachties use it too. https://fi.google.com/about/