You can contact any service provider and the details of Data plans.

You're correct that you cannot bring your own phone to Boost Mobile, you must use one of their phones, and it is the same with Virgin Mobile.

If you are just looking for a decent data plan, T-Mobile has a $30/month 5 GB plan with throttling after, unlimited text messaging, and 100 minutes.

If you need more minutes, but less data, you can look into other providers such as Red Pocket Mobile which uses AT&T's network or Ptel Mobile.

I am going to have to cancel my existing Verizon iPhone 5 plan due to some personal issues and since my phone is unlocked I'm able to choose another plan from another carrier and continue using it. I've checked T-Mobile, AT&T, Sprint, Virgin Mobile and Boost Mobile, and I think Boost Mobile's 18-month shrinkage unlimited plan is really good, but the website simply gives me a feeling that I will have to BUY a phone from them in order to use their service. Any help is appreciated, thanks!