Sprint account spending limit?

I purchased an iPhone with sprint as my carrier about a month ago. My spending limit was $150.00. I paid my first bill on June 23rd ( it wasn't due until July 3rd). When I logged onto my account today, it said that I didn't have a spending limit. What does that mean?

That is the amount that Sprint puts on your phone because of either 1: you have bad credit or no credit. 2. Once you hit that amount because of a missed payment then the phone shuts off.