Store procedure problem

Hej .. jeg har et problem med en stored procedure i min mssql 2005. Det virker fint i en lignende funktion, hvor jeg benytter en int som input. Det virker os fint hvis jeg indtaster/hardcoder Engros ind i:
WHERE type_company_tob = 'Engros'.
Men af en eller anden årsag, så benyttes variablen ikke i min stored procedure.. hjælp! :) Har vedlagt både koden fra min webservice og stored procedure fra db.

---> Webservice:
SqlConnection conn = new SqlConnection(connectionString);

            SqlDataAdapter da = new SqlDataAdapter("[t9User].[GetCompanyTypes]", conn);
            da.SelectCommand.CommandType = CommandType.StoredProcedure;
         
            SqlParameter paramPAF = new SqlParameter();
            paramPAF.ParameterName = "@companyType";
            paramPAF.SqlDbType = SqlDbType.NVarChar;
            paramPAF.Direction = ParameterDirection.Input;
            paramPAF.Value = companyType;

            da.SelectCommand.Parameters.Add(paramPAF);

            DataSet dsCompanyTypes = new DataSet("CompanyTypes");

            conn.Open();
            da.Fill(dsCompanyTypes);
            conn.Close();

            return dsCompanyTypes;


---> Stored procedure:
set ANSI_NULLS ON
set QUOTED_IDENTIFIER ON
GO
-- =============================================
-- Author:        Peter Overgaard
-- Create date: April 7, 2007
-- Description:    Get company types of Detail or Engros
-- =============================================
ALTER PROCEDURE [t9User].[GetCompanyTypes]
    -- Add the parameters for the stored procedure here
    @companyType nvarchar
AS
BEGIN
    -- SET NOCOUNT ON added to prevent extra result sets from
    -- interfering with SELECT statements.
    SET NOCOUNT ON;

    -- Insert statements for procedure here
SELECT id_tob, type_title_tob, description_tob, type_company_tob
FROM type_of_business_tob
WHERE type_company_tob = @companyType
END