http://venturebeat.com/2012/08/08/burner-phone-numbers/ Burner lets you buy a number to use for a certain amount of time before it's "burned," or goes inactive. http://burnerapp.com/ The app is free on iOS, but the numbers are not. Users buy "credit packs" that range from three credits for $1.99 to 25 credits for $11.99. You can then use your credits to load various Burner "types" on your phone. For instance, three credits will get you the "Mini Burner," or a number that expires after seven days. Eight credits will get your a Burner number that expires after 30 days.