I'm looking to build an SMS verification system for new registrations on my vBulletin site

I'm looking to build an SMS verification system for new registrations on my vBulletin site. The workflow should be: 1. A user registers for an account. 2. My vBulletin forum site asks for the required info such as username, email address, etc AND a phone number. 3. The forum sends a 4-digit one-time-password to that phone number (the message will be in a non-English language). 3.1. The forum should send the OTP only if the user passed the questionnaires (vBulletin already has this) to prevent sending out SMS without necessary. 4. The user needs to enter that OTP to finish and activate his or her account. I'd also need a few couple other functions as well: - A feature to ban certain phone numbers from being used for registration. - A feature that prevents an existing number to be used again for registration. One more thing, since the vBulletin forum software, will be updated from time to time, the modification has to be something modular, can be added to the new versions/updates easily. For the SMS Gateway, I have [login to view URL] in mind but feel free to suggest a better one if you'd like to.