Rest Service Not Getting called from Mobile App for Long Text

I have Created WCF Rest Service for Mobile App Exposed with Post Method.

In that user has to send Long text. Like 40,000 characters. till 900 Chars it works fine if it more than

that it Gives Error.

"Request URL Too Long

HTTP Error 414. The request URL is too long."

My Code on "ABC.SVC" files

Public Sub Text(ByVal strVersion As String, ByVal strKey As String) Implements IMobileApp.Text
End Sub

In Interface

<OperationContract()> _
<WebInvoke(Method:="POST", RequestFormat:=WebMessageFormat.Json, ResponseFormat:=WebMessageFormat.Json, UriTemplate:="/Text?Version={Version}&strKey ={strKey }")> _
Sub Text(ByVal Version As String, ByVal strKey As String)

What changes I have to do . so It get called for any long text.