How to get my t-mobile service to work on my iPhone 5s?

I just got a new iphone today & I already set it up with the SIM card. It says T-Mobile in the left corner & has bars as if I have service but when I go to send a text it doesn't go through or when I go to call someone it just calls T-Mobile. How do I get service? I tried calling t-mobile but their calling hours are over now.

May be they haven't activated the service yet. Take it to the T-Mobile store or call them and it will be taken care of in a minute or so.

If you have activated the SIM card already, you may just need to turn off the phone and turn it back on after about 30 seconds.
This is what the representatives normally suggest is to do whenever they make changes on our service