iPhone: this accesory is not made to work with iPhone?

I have an iPhone and couple days ago I started getting the message this accesory is not made to work with iPhone. I tried everything like a full restore on iTunes and resetd couple time still no luck. There is nothing connected to it. I cleaned it with compressed air and still no luck. I took of to apple store yesterday and they looked at it and said they found liquid and its not covered by apple care. I havent ever dropped my phone in liquid before. Apple wanted 200 dollars just for them to open the device and clean it out. I was wondering what I can do to make apple accept this device so they can fix my problem? I can't go backto apple store because its to far were I live. I also want to know if I can send it into appple through there online service? Thanks to all who help