I use ATT. It's fair. It gets the job done. I use a Samsung S7 phone that I bought here on the forum from @avguytx . It's been really good. It's a few years old now. I wonder if he has a newer phone for me to buy lol. Smart Flip phones are out, but very expensive.
My dad is 81. He uses an ATT plan where you pay $100 for 1000 minutes. They sold him a flip phone to work on this plan too. When ever he needs more talk time, he stops by there and hands them a hundred bucks + tax.