Unable to send text, getting error 500

Hello @Suppapumpa.

We'd be happy to help with your wireless messages.

While the Honor View 20 has been released and is being sold, there currently aren't any plans to bring the phone over to the United States.

Have you already checked the devices compatibility with our network?

While the device may be compatible with the network, it may not be compatible with AT&T's LTE network.

For further assistance you will need to reach out to Huawei's support team at 888-548-2934.

Vincent, AT&T Community Specialist

The phone is compatible, I've been using it on AT&T lte for around a year. I found the issue was the SMS Center Number was incorrect. I put the correct number and fixed the issue. 

Hi @Suppapumpa.

We're happy to hear that you were able to resolve the messaging concerns you were experiencing.

Thank you for choosing AT&T.

Vincent, AT&T Community Specialist