I was caught out around a month ago when One UI updated my phone. I use a physical SIM for calls and text, and an eSIM for data. The One UI update changed the setting for the data eSIM to be the physical SIM. I noticed this when all of my pre-paid "pay as you go" credit disappeared. I entered the odyssey of trying to get help from Samsung's online chat - ideally discovering what I might have done wrong to allow a simple update to cost me a not-so-insigificant amount of cash. Seriously, if you ever need help, chat isn't the place to get it. I was wounded but not defeated, paid another pile of pay as you go cash to recharge the physical SIM, fixed the setting that Samsung changed for me and went ahead using my phone.
A couple of days later, yet another One UI update came through. I was wise enough to check if Samsung had again done what they did before and sure enough, the physical SIM was again made to be the data SIM. I lost a couple of dollars just while doing the switching (the data costs on the prepaid SIM are crazy) but I caught it before all of my credit was gone.
Around a month later (yesterday) One UI was updated again. Surely Samsung will have fixed their very costly error by now. Nope. I foolishly had faith in the Samsung engineers and I'm again out a not-so-insignificant amount of cash.
Please fix YOUR ERROR Samsung and stop (essentially) charging me many tens of dollars to keep my phone updated.
