Using your phone to confirm your account is an optional step.
When one sets up an account, the first thing is link and confirm an email address. Next, in order to complete the verification process, you should link and confirm both a bank account and credit card. Doing so removes your limits, gives you a back up funding source and in most cased validates you are who you say your are.
Adding your phone is an additional step for Setting up your Security Key and provides an alternative method for receiving funds. If your phone is not active yet, all you can do wait until it is, then complete the process.