my phone got wet now it wont turn on

Some have found that putting it in a zip lock bag with uncooked rice for a week helps dry it out. Do not try to turn it on or charge it until it has been there long enough to dry out.

If it still will not work you need to go to an Apple store genius bar for an out-of-warranty replacement, for an iPhone 4 that is $149 in the US.

Moisture and electronics don't mix.

If you want to continue using an iPhone, get your wallet out.

Apple offers an out of warranty or not covered under the warranty "repair" price which pays for an exchange for the same model/color/storage capacity at a significantly reduced price off the full retail sales price without having to sign a new contract with your carrier.