Why can't I get service on my iPhone 4S?

I just came back from a trip to Phoenix. I turned off my mobile data and turned airplane mode on. Both of them remained that way until the trip was over. I was there for four days. I came back to Winnipeg and turned them back to the original settings. It's been a day and I still don't have service. I tried turning my phone off and then back on again, turning the mobile data off, and turning airplane mode on. None of them worked. I don't know why. My brother has service and he told me to try these steps.

My carrier is MTS. Can you please help me get service?

You should contact your carrier… They will most likely know what's the problem and could help you.call them from a land line phone

Take the sim of the phone out, reset the phone settings, put the sim back in and wait for signals