Can a bad SIM card cause LTE not to work?

[iModFrenzy]

So I called AT&T about my iPhone 6S not getting LTE service. Only 4G. This all happened after I updated my phone to iOS 10. So I went back to iOS 9.3.2 and I'm still receiving the issue.

I tried resetting network settings, having AT&T reactivate my phone,etc

Now they said that my SIM card could be faulty and that's the reason, I also can't Wifi call for some reason even tho it's enabled.

Thanks

 

[Gav2k]

Yes a bad sim can cause the issue

 

[iModFrenzy]

Yes a bad sim can cause the issue

Ah okay

Do you know why exactly? I'm confused as to what could happen to the sim that would cause this. Cause it was perfectly fine before I updated to iOS 10

 

[Gav2k]

Ah okay

Do you know why exactly? I'm confused as to what could happen to the sim that would cause this. Cause it was perfectly fine before I updated to iOS 10

Have you gone to setting general about to prompt the phone to check for a carrier update? That could be the issue but it may just be the sim was on the way out and the update pushed it over the edge.

 

[iModFrenzy]

Have you gone to setting general about to prompt the phone to check for a carrier update? That could be the issue but it may just be the sim was on the way out and the update pushed it over the edge.

I have not prompted it for a carrier update, just going to Settings>General will prompt it?

Oddly the same thing happened to my iPhone 5, stuck on 4G 24/7.

I'm not too experienced with this but can APNs be of any help?

 

[iModFrenzy]

Okay so no carrier updates, I didn't think APNS would do much (they didn't) .