Microphone issues on iPhone 6

iPhone was in water and sand few days ago and now microphones are not working. I tested all 3 microphones with Auphonic app and by recording video and all of them sounds like someone blowing air directly to microphone.

On bottom microphone my voice is barely heard.

On top front and top back microphone there is just strong wind and nothing heard even when i shout right at the microphone.

I tried cleaning microphones with tissue, cloth, toothpick and even a sticky gum but no difference.

I want to know how can i fix it. Any help is appreciated :)