@nprofile1q... My guess is that you're in the states. I had a similar situation with other second hand online stores. I did find a cheat workaround if you need their service after all.
Purchase a "try me" sim card from a pre-paid mobile provider, loads of them out there, and it usually come with a short trial mobile number that you can use to register. But also register an temp email which you can always re-deploy at any time.