As far as bringing over your existing phones - you'll need to confirm that they are unlocked through whatever plan you are thinking of using. If they aren't unlocked, doesn't matter what you want to use; they are bricks for you if you want to leave your current provider. Pretty sure you have to use a network compatible phone too, so like a Sprint compatible phone for a Sprint coverage area provider (like Ting), but that may have changed since I joined up with my phone service (it's been a few years).
So I have Ting, and iphones work just fine on it. And as it utilizes the Sprint network which you already use, you know the coverage works for you.
It may not be the cheapest for your situation, but your requirement to use iphones (preferably your currently owned ones) is going to mean you can't go someplace like Google FI or Republic Wireless, and cost you much more than being flexible about the phone, and the high data use requirement is going to cost you as well. Learning to cap your own data and being smarter - using free/available wifi first choice and maybe forgoing data usage unless really necessary - will save you so much money in the long run. And there is a large amount of free wifi out there if you're desperate to check a website or stream something.
So for Ting,you can check here based on your assumed/average use:
https://ting.com/ratesNo contract, you most likely can bring over your phone (you can check that on that same link) and you pay for what you use each month. You very likely could use MUCH less data than you currently do right now since we tend to get lazy about it when it is unlimited. If you start slowing down on the amounts and aren't a crazy 1K/month texter/streaming on data and utilize free/available wifi more often, you could see a total bill of under $50 for both phones. And their customer service has been stellar for me (Ting is a
great company).
If you do end up going with Ting, they have a referral program too - see my signature for my code. You get $25 off when you sign up (and I do too - you can share your own code with friends/family and you'll get the same deal for as long as anyone uses your sign up!)
I believe that Boost Mobile’s $35 a month plan (so around $70 total) includes unlimited talk/text and 3GB of 4G LTE data per line are Sprint's MVNO solution. Cricket is ATT and they offer similarly priced plans. In both places, you'd need to check your phone's ability to port over.
