I pretend to be on the phone so I don't have to make friends
Why do you feel the need to be on the phone?
Because people usually don't pay much attention to you
If others want to talk, then you should make an effort to engage with people and have a conversation with them. Staying on your phone might cause them to view you as being rude.
It's fine, I'm hardly going to talk to them and they wouldn't care if I was rude to them.
Well, if you are in a situation such as on a public bus, where most people wouldn't expect to interact, it's fine to pretend to be busy.  However, if you are at a social function, it would be quite rude to ignore others, and you should at least be civil with them.