it’s rude to give too much attention to your phone when you’re talking to someone

I hate when someone is busy with his phone while I'm saying something important and he'll be like 'were you saying something?' making me repeat my statement all over. Because I hated this, I resolved not to do it to others hoping they'll learn from me. It's been difficult but I've seen the fruit already. Recently, someone noticed that I don't pay attention to my phone while I'm in a conversation and he saw sense in it and he wants to start doing the same. Good manners is contagious too