I have an iphone 5s, I will be making a long drive here shortly. Thing is, my iphone is blocked so it gets no service signal. I want to be able to use wifi at home and get my route for the drive. Is there anyway to disable the rerouting feature? When I stop at a rest area/food/gas station, I don't want it to try rerouting and end up not being able to(because of no service), and end up loosing my GPS directions.