Can I be on the phone for three hours of a ten hour bus trip?
What will you be doing on your phone?
I will be playing games.
There's nothing wrong with playing games on your phone in public as long as you are quiet and don't disturb those around you.
I don't see why it would be a problem anyway.
Use headphones or have the sound off so as not to bother the other passengers on the bus. I'm sure it won't bother anyone and most people would prefer to be left alone anyway while travelling.