Simcard not detected on a Samsung Galaxy S

My phone is a Samsung Galaxy S4 and it's not able to recognize the simcard inside it. I reseated and made sure it was properly inserted into the slot then turned it on. The simcard was still not being detected so I tried another simcard and it did not make a difference. What is wrong with my phone? Is there anything I can do to fix it or should I just take it back to the carrier and make them fix it?
