Phone Apps on Cell Phones

I have never used anything other than the Google dialer or whatever it's called but if you look around on the fdroid store there are some alternate dialers that may or may not be helpful. Simple dialer is what comes to mind but again I've never really looked at any in depth. Not sure if they're allowed to handle answering calls, you'd probably want to experiment with them on your phone first and see what you can do. Past that, your uncle may be a candidate for one of those dedicated old folks phone (jitterbug or something of the sort). Also possible there exists a phone rom built for purpose to be simple for older folk but that's just speculation and may be more work than you're interested in taking on.