Change your SP in that way:
ALTER PROCEDURE InsertData
(
@firstName varchar(50),
@lastName varchar(50),
@year varchar(50),
@school varchar(50),
@city varchar(50),
@state varchar(50),
@country varchar(50),
@e_mail varchar(50),
@mobile varchar(50)
)
AS
BEGIN
IF EXISTS(SELECT PersonID FROM Person WHERE Mobile = @mobile)
BEGIN
SELECT PersonID FROM Person WHERE Mobile = @mobile
END
ELSE
BEGIN
INSERT INTO Person (FirstName, LastName, Year1,School,City,State,Country,E_mail,Mobile) VALUES (@firstName, @lastName,@year,@school,@city,@state,@country,@e_mail,@mobile)
RETURN @@IDENTITY
END
END