Where can i use my unlocked sprint iPhone 5s?

I just bought a unlocked sprint iPhone 5s and I looking for a good place to set up a plan the plan has to be under 50 a month please help

Virgin mobile. Runs on sprints network but is prepay. 35 a month for unlimited text and data and 300 calling mins. 45 for the same and 1200 calling mins and 55 a month for unlimited everything.

You can only use it on CDMA sellers in the United States (that means carriers like Sprint, Boost, Virgin, etc). Because it is a Sprint iPhone, you won't be able to use AT&T, T-Mobile, or Verizon even though it is "unlocked".It is only unlocked for international carriers.

Here is a great video about unlocking iPhones that you should check out. Fast forward to 6 min 43 sec to the Sprint section, I think it should help clear up some questions: