Buying a phone number is an integral part of the Twilio system. If you have multiple users, you can assign each user their own phone number.

Twilio gives you options to pass on numbers to your users, so you can actually search for phone numbers.

You can search by postal code; patterns, such as STRINGER; or for phone numbers near your location.

I've found this ability handy for systems with multiple users or for setting up business numbers for various purposes, such as sales, support, or unique phone numbers for campaigns that are being run at the time.