You want a dumbphone - of which your options are going to be like phones that specifically lack browsing/internet features like Tracphones or Nokia phones. (Another alternative is like the Sunbeam F1 or various Japanese dumbphones)

Alternatively, you could just buy a cheap Android phone and use ADB to remove those features (like the built-in browser and wifi) you don’t want.

link but the subreddit for dumbphones is an excellent resource: https://old.reddit.com/r/dumbphones/comments/zpw77o/state_of_the_dumbphone_2023_read_this_first/