Q: After updated to IOS 9.3.1, my Iphone 6s plus have problem

After my Iphone 6s plus updated to IOS 9.3.1, my Iphone have some problem, yesterday my Iphone suddenly can't connect to my carrier service, keep pomp out no service this word, yesterday morning still can use it, but afternoon it can't connect to carrier service. I think maybe is my sim card problem or my phone problem, so I try restart my device and try take out my sim card and put it again, but still no working, So I try change my sim card to other device, i found that it can use at other device. So is my device problem, but my Iphone just buy almost 2 month only, and i never drop my phone, why so fast have problem? i also found that after 1 day, my device can connect to carrier service, I think it will fine, but the problem come again, suddenly can connect carrier service suddenly can't connect of it, so what the problem of it? I hope can solve my problem.