Will I have to get a new phone?

My phone network stopped working and caused my phone to not do anything I tried powering it off my friend even looked at it to see if something wasn't turned off, but nothing worked. I tried to send messages and things again because that's where the problem started occurring but they still wouldn't send. I finally just reset all of my settings and nothing happened at all. I do have this major crack on the back of my phone that I got from dropping it over the summer and it's pretty bad b/c I can see part of the inside of my phone but not a lot. I don't really know what to do besides going to T-Mobile to get it looked at or just get a new phone entirely.