Why does my phone fail to charge

Hi,

I dropped my phone in water a day ago. It worked fine at first (except for some stains under the screen that went away during the day), and I used it for about 12 hours until the battery died. After that, I noticed that it didn’t charge, so I took it to a store for diagnosing.

They told me I needed to change both the port and the battery, since both were damaged. I put the battery in another phone just to check, and it charged just fine. I told them about that, and they said that the battery was damaged anyway, and that it would work for other phones, but not for mine. I figured that they were being dishonest, since what they said sounded illogical, so I chose to only replace the port, after which the supposedly damaged battery charged very well.

However, right now, after the battery has died, it isn’t charging again. Could you please help me understand what might be the problem?

Thanks!