My iPhone does not receive mobile signal, keeps "searching" indefinitely

My iPhone 4 had a small incident with water, after put it in rice and a few days of drying it works great. The only problems seems to be the antenna that doesn`t seems to receive the mobile signal. The Apple Store in my country (Venezuela) told me that it has no repair. But didn`t even inspect the device. Wifi and bluetooth works fine, as everything else. I`m travelling to the States in a week and I thought you might help me.