Phone won't make or receive calls

Yeah I'll try to get to a store with the hubby tomorrow,  just really frustrating since the phone really isn't that old and I'm in the middle of trying to buy a home.   I appreciate your help though,  thank you. 

I have an unlocked Samsung Galaxy S9+ and it is acting the same.  Called customer service from my work phone and she tried all she knew but nothing fixed it. I restarted multiple times, even tried safe mode, nothing changes.  I got a new sim card. The rep used my phone to make a call and it worked.  Got to the parking lot and tried to make calls but can't. Went back in the store and he said there's nothing else I can try. Spoke to another customer who has an unlocked galaxy S10 and he said he had to get a new phone.

@shannaschueller 

Check your APN settings on your phone,  also was it bought unlocked or is it unlocked from another carrier? 

@Timbeh0617 I bought the phone already unlocked from Best Buy. What is APN?

I had same problem start yesterday cant make/receive calls but can txt. Tech support much troubleshooting then tried resetting "activation" worked briefly. Now next day same prob. I am thinking some kind ofvauthentication error their end so may try new sim. Tried everything else. Samsung 6s edge plus on approved list.

I have a Galaxy S5 active. Since they turned off 3g yesterday I'm unable to send MMi  codes to check account balance and usage. Try sending *3282# from your dial pad and see if you get the error message.

If you have the option to switch Enhanced LTE Services on & off, switch it on.

I used to have it off to save battery power but when they turned the 3g off I couldn't make or send calls until I switched it on. The downside is it uses about 2x battery power in standby.

I have the same issue. I just went to an AT&T store by me and the worker said they've had about 40 people come in this week with the same exact issue. Can't make/receive calls, but texts and everything else work fine.

I have a Galaxy Fold 3 w/ First Net Service. I received my last phone call about 21 hours ago. Nothing since then.

So after trying everything yesterday my hubby took out my sim card and put it back in and now it's working.   We will see how long it lasts but worth a try for others.   Wasn't on the list of fixes though I feel dumb for not giving it a try. 

Edit:  just as predicted the fix was temporary.   Back to no calls.   (Admit it's nice not having to deal with my extended warrantee calls lol) 

I am having the same issue with my ASUS phone with ATT sim card. I had this issue before and they fixed it. Today nobody seems able to fix it. Text and data work. I am really disappointed with ATT service lately .

My other sim card on the same phone (T-mobile) works fine.

Let's work together to figure out what's happening with your service, @blkopns.

As mentioned by @Timbeh0617, the 3G phase out may be the cause of your service interruption. Please reply back with your model number, and we'll look into this further. 

A few things you can try to restore service on your device is:

• Check for software updates (From the device home screen, pull down the notification shade and tap Settings> Under the System category, tap About device>Tap Software update>Check for updates> Follow the on-screen prompts to download and install the update.
• Check to make sure LTE service is enabled in your settings menu. (Go to Settings> Connection> Mobile networks> Enhanced LTE services and select ON)