Why I can't make or receive calls but data and text messages are working fine?

[AC Question]

Hello everyone,

I have a Samsung Galaxy S3 and it's been almost a week since I can't make or receive any call. However, I can send and receive text messages and the data is working great.
I called customer service and they told me that there's nothing on my account and that it must be something with the phone settings. Then, I took my phone to two different AT&T stores. They checked again my account, changed my SIM card and did a reset, but nothing worked and they do not know what is wrong with my phone.
I haven't give up so I checked again the settings and I noted that it says "Mobile Network State: Disconnected", and when I try to choose the network, it doesn't let me... It should be something I can do...

Could anyone please, help me with this? Thank you!!

 

[Rukbat]

Bring the phone back to your local AT&T Device Support Center. (Ask at the local store if you don't know where the DSC is.) Point out the "Mobile network State Disconnected" message to them. Since it works to text, it should work on voice, since they both use the 2G radio.