All VRS providers in the U.S.—including Convo—are overseen by FCC and therefore must comply by its regulations.
Under Federal Communications Commission (FCC) policy, video relay service (VRS) can only be eligible for deaf, hard of hearing, deafblind, or speech-disabled people. The last four digits of your social security number are the best way to verify your identity to ensure that you are eligible to receive VRS.
If you don't have a SSN, there are alternative documents for you to submit.
"I'm hearing. Can I get a VP number?"
For hearing people interested in getting an account with Convo, FCC will begin a trial period in which VRS providers are able to give videophone (VP) numbers to hearing people with only point-to-point calling capacity. This means hearing people with VP numbers can only call other VP users directly, but not use VRS.
You can see FCC's FAQ on this topic in ASL videos here.