BAS supports phone verification through one of following services: http://smspva.com, http://sms-reg.com and http://sms-activate.ru.
Module interface looks like this:
Phone activation procedure has following steps:
Optionally you can call “Enable debug” action to see which API requests BAS does.
All activation services use same interface and same actions, so you let script users deside, which service they want to use and don't change your script!
Here is minimal example - phone activation for twitter.
Video: