You can check whether CNAM lookup is configured for your US phone numbers on the console or via the API.
Checking CNAM lookup status on the console
Go to Phone Numbers > Active to see the CNAM lookup status on your US numbers.
You can also filter numbers by CNAM lookup status on the console.
Checking CNAM lookup status via API
Use the cnam_lookup parameter of the AccountPhoneNumber object to check via API whether CNAM lookup is enabled.
You can filter numbers by using the cnam_lookup parameter in the List Account Phone Number API.