Not able to make or receive calls with new sim card

We'll be happy to assist you with your reception concerns @hurstdenise.

Since the shutdown of our 3G network, some non-AT&T devices active on our network are no longer working. While we work to resolve this, you can try the following solutions that have worked for some customer:

• Try turning Airplane Mode on for a few seconds then off again. This will force a connection to the nearest tower.
• Try resetting your network settings. To do this, go to Settings > System > Advanced > Reset options > Reset network settings.
• Make sure your device software is up to date.
• Visit an AT&T store to get a new SIM card.
• Program your device's APN settings:
  • Tap your Settings menu.
  • Choose either Wireless & Networks, More Networks, or Connections.
  • Tap Mobile Networks, then Access Point Names.
  • Find and select the option to add a new APN. You may find a plus (+) symbol on the screen, or tap the menu button.
  • Program each field using the settings found in the table.
  • Save your changes to return to the APN's menu and choose the new APN.

Please let us know if any of these solutions worked for you. Thank you for reaching out to our AT&T Community.

Darais, AT&T Community Specialist

It is beacuse your incoming is switched off. I have also faced the same issue. For solve this call to the sim provider company and tell them all the issue you have faced. They will switched on the incomming. Also, you can go to the service provider office, they can also solve your issue in no time. 

@hurstdenise

Which model A71?

The only unlocked model is the USA Galaxy A71 5G (A716U1)

If you have a different model number, it cannot work on AT&T. If this is your model number it is missing a software update that will allow it to function on AT&T