Capturing phone numbers for text blasts

[Jeff Sheraton]

I currently have a dedicated number (google voice) people call when they see a property of our that they would like to rent.  

I am trying to figure out how I can capture the numbers that call my number and create a database that I can then send text notifications to about new properties.  Ideally on this system people would have the option to opt out of receiving future messages as well.

Any ideas?