have you tried to not use Boolean. Try instead number 0/1 or varchar2 Y/N.
Not Available in ODP.NET, Managed Driver
PROCEDURE PROC( pNumber IN VARCHAR2, pTable OUT tCliente, Existe OUT NUMBER) IS
Oh, i see now that you have OUT object called tCliente what is it? Describe it.
You're specifing your OUT parameters with direction "ReturnValue" (in the C# code). Maybe you have to use OutParameter here?