So, My experience has been rather confusing, but pleasant with the MVNO FreedomPop. FreedomPop can use cdma or gsm unlocked phones, and they use a sprint signal for cdma phones, or a tmobile signal for gsm unlocked phones.
I can’t use FreedomPop because both of my mobile phones are gsm and carrier locked, meaning that the phone company has restricted me from using their phones on another gsm network. Also, the phones can’t use a cdma signal from Sprint or Verizon.
When you buy a phone on installment, it is locked to the carriers network, and will only accept a sim card from that carrier.
So, both my current personal phones can’t use any other sim card other than a t mobile one. But that is acceptable because I use google voice, and I’m ordering a new phone from another carrier. T mobile is just too expensive, and an MVNO with a cheaper handset, sim card, and plan just makes more sense for some people.
My advice to you is to never buy an carrier locked phone, and never buy a phone on installment, and buy gsm if you can.