Is it possible to change the function of a key on a cell phone?📱

My mom recently had to get a new phone because her phone was an older model and would no longer be compatible on the 5 g network.

She has an AT&T Cingular flip.

I'm trying to customize and reassign what certain keys do. I believe this is possible on some phones, but is anyone familiar with how to do this?

I've already googled like crazy. Thanks in advance.