How to get by with a water-damaged iphone?

I accidentally dropped my iPhone in water for 4 seconds and took it out quick. I let it sit to dry for 48 hours and it turns on with the Apple logo and then it shows a wrong date (12/31/2012) a few times before going to the right one. It shows the menu and all but I realized the Wi-Fi signal is acting up (it switches on and off so I had to manually turn it off). The biggest problem was the signal with the 5 bars. It mostly showed "Searching… " for a few minutes before shutting off by itself. Please note that after 48 hours the only way to turn it on was charging through my external battery case. I tried charging it through my macbook but it only shows the Apple logo. My dad told me to do research and find options to fix it but I'm afraid that nothing else will happen and that I have no other choice but to buy a new phone. What should I do?

Added (1). Please note that my contract ended and that i had this iphone for 3 years. But it sounds like my dad really wants me to fix it but i literally just want to tell him that i need a new phone.

I would try to get it replaced at the Apple store

I would say leave it alone for a bit longer or put it in rice… If it continues to act up take it to Apple and try to get it replaced. And don't tell them you dropped it in water, tell them it randomly started acting up like this. That's how I got mine replaced! XD