Iphone 5 Sprint

Good day i have an iphone 5 from sprint with ios 6.1.4 i want to upgrade to ios 7.1.2. I have been using rsim 9 pro and no problem at all. Is it safe to upgrade??? i want to be fully functional calls sms and 3g. In case rsim9 pro doesnt work If i have to buy rsim air2 or rsim 9 nano cloud its ok but want to make sure everything works just fine.

Thank you

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