Does phone-walled mean you have to verify with a phone number? Are you unable to do it because it doesn’t work, or because you don’t want to give it your phone number?
Since you need to provide a phone number to sign up for Discord is the reason I never will.
There should be no reason for a phone number and nor do I want to waste my time trying to buy pass it with internet provided single use numbers.
Unless it is a service I must use, then I will provide a phone number. If it is a service I get to choose to use then I will never provide a number.
Most likely they don't want to. It's ridiculous that you would need to give your phone number for some chat program.