How To Find Serial Number On Net 10 Zte Whirl Android Phone.

I lost activation card, activated over 2 month ago, late adding refill card, now i cannt reactivate my phone to add minutes/ data.how can i reactivate my phone, i tried to reactivate phone online, was told serial number not recognized, what now? net 10 needs to make paying/ putting refill cards on much simpler' loved my phone but now unusable, have to go back to verizon, verizon is best service and more user friendly phones. hope they get more budget friendly android phones, im going bak to verizon, also you have to call from a second/other number yo activate net 10 anf straight talk, very inconvenient.