If you're already receiving lousy reception/signal from Virgin Mobile, chances are you'll receive the same quality reception/signal with the iPhone. It won't really change. The only difference I can see is if you live in a major city where Sprint LTE is available. That would give you faster speeds, but their coverage is very limited. You're better off buying a used iPhone 5C for either AT&T or Verizon. There are plenty of prepaid services that use their network and are much more affordable (Straight Talk, Net10, Page Plus, H20)
I suggest you buy a tmobile iPhone 5C since tmobile has great and fast service. Virgin Mobile and T Mobile both have the iPhone 5C at the same price. The only difference is that T Mobile iphone 5C can become unlocked after 40 days which means you can use with more carriers other than T Mobile. Also T Mobile has great plans as well. For example I use the $30 unlimited text and 5GB data with 100 min. There's also $80 unlimited everything in T Mobile with no throttle. So it's your choice do you want crappy internet speeds (Virgin Mobile) or reliable service (T Mobile).
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