iPhone 6 can't access cellular data
I recently got an unlocked iphone 6 and have been working to transfer everything over from my 5s, including the sim card. When I move them sim card over, everything works just fine as long as I am connected to wifi. Once I am not, however, I cannot access cellular data, send and receive calls or texts, or access the internet. What do I do to be able to get service on my new phone?