Wi-Fi Antenna Problem

Hello, so about 2-3 months ago i dropped my phone in the toilet, I didn't think anything was wrong with it and i immediately pulled it out of the toilet and did not soak out the water with rice, now I am stating to experience problems that I did not have before I dropped it in the toilet. My phone will not connect to wifi unless my device; iPhone 6 is right beside/in the same room or directly above/below the wi-fi router, if I move to the room beside the router, it disconnects, anywhere that is a few metres away from the antenna, it disconnects. This is extremely frustrating considering I will have 0 bars while people beside and around me have 3 bars and full connection. I am looking to go repair my iPhone but I would like to know where the best place to repair it is and the approximate amount it may cost. I have a nearby walmart that fixes phones but should I go to the apple store instead or does it not matter? Thank you for your help I hope I can find a clear solution to this problem, and if the wifi antenna may not be the problem, what would it be? 🙂