Nope, most people do have unlimited data plans. And unless you live in some tiny, mountainous, Eastern European backwater, the plans aren’t actually that expensive either. And even if you truly are a time traveler from the year 2002 like you appear to be, and you have an incredibly limited 5GB data plan, you’ll be happy to know that even if you reach your data cap, you will still have data connectivity enough to use RCS without issue. All that happens when you “run out” of data on phone plans is you’re throttled down to a slower speed that is still more than sufficient to sent text messages over RCS.