Galaxy S9 stopped making and receiving calls

@loucacc967 Hello.  I won't pretend to be an expert or anything here. 

I have been dealing with bringing international devices purchased from third-party vendors...such as Amazon and eBay...to various networks and and getting them to work for over two years. 

As others here will soon tell you.. At&t has provided a whitelist...or actually two separate lists of devices that they claim are guaranteed to work on their network. 

One list is of phones that At&t sells..or branded devices. The other contains unlocked..or carrier free phones.

Even if your phone is shown on either whitelist... it doesn't mean that it will work.

At&t has set certain criteria that it claims a device needs to be compatible with the network. And only the exact model number shown on the list is compatible. 

So even if you have the same model name of phone...such as the Samsung Galaxy S9... it has to be the exact same model number that's listed... to work on the network according to At&t. 

Depending on where you purchased your phone...and what model number it is...unfortunately your phone may not be allowed work on AT&T.

I recommend checking the whitelist before considering changes carriers. 

As far as whether Consumer Cellular can help...I have never used them for service...but I can speak to my experience dealing with another similar carrier Straight Talk.

Each of these carriers are what is known as a Mobile Virtual Network Operator..or MVNO. 

Basically that means that they lease the use of the cellphone towers... that are owned by the major carriers At&t, T-Mobile, and Verizon. 

Some in this forum say that these MVNO have the ability to help resolve this type of issue...however in my experience they were not...and the two devices that were with Straight Talk were taken to T-Mobile... and so far..have had no issues and are fully functional. 

Depending on what towers Consumer Cellular uses for service...will also determine what other carriers you may be able to take your phone to. 

As I said I have never been with or used Consumer Cellular...so I can't say specifically which ones they use. 

@loucacc967  As far as your phone itself...here is information that I found...from one of the online sources I use... to learn more about the specs of the a device before I buy it...to check for things like compatibility. 

I will say...as others in this forum will... none of the information listed below will guarantee that the phone will work with AT&T... or any other carriers. 

According to the information listed below...every variant of the Galaxy S9... including the five manufactured for use in the US... is VoLTE capable. 

Another important factor is the feature HD Voice.  Every variant listed has the feature built-in. At&t claims that many devices are not capable of using the feature with their network...or don't have the ability at all. And AT&T claims that this HD Voice feature is key for a phone to work with the network. 

At the moment...at least one carrier doesn't have such restrictions for HD Voice. 

However... none of the major carriers have completed their 3G shutdown... although most people who post here say that they all have started. 

At&t latest 3G shutdown date is March 31-April 1, T-Mobile June 30-July 1, and Verizon December 31. So there is a chance that the other carriers could implement the same restrictions as At&t. 

At&t claims these restrictions are necessary due to the 3G shutdown/5G upgrade... and a FCC requirement that all phones are able to be located on a e-911 call. The e-911 FCC requirement is true... but it remains to be seen if the HD Voice feature is apart of those requirements. 

I hope this helps.

I have the VoLTE problem also. My Samsung S9

does not list a VoLTE setting. I was using it on AT&T network and purchased from AT&T originally. When I switched to Consumer Cellular the text messaging would work but the phone would not. Consumer Cellular said it is a problem with the AT&T network which is strange since that is the service I was using.