Data type Conversion error when running a select query with a SUM() function agaignst database.

ALTER PROCEDURE dbo.GetSupportHoursByCompanyID
@CompanyID int
AS
      
      SELECT     SUM(ticket_support_time_used) AS SupportUsed
      FROM         tbl_ticket
      WHERE     (company_ID = @CompanyID)
      
      RETURN

After running the above Stored Procedure  i get the following error message from ASP.NET:


"Error converting data type nvarchar to int."


My Database code looks like this:

public List<Ticket> GetSupportTimeforCompany( int companyID)
        {
            // Create Product collection
            List<Ticket> colTickets = new List<Ticket>();

            //Create an instance of the DataManager Class to get the connection string.
            DataManager ConnectString = new DataManager();

            // Create connection
            SqlConnection con = new SqlConnection(ConnectString.GetConnectString());

            // Create command
            SqlCommand cmd = new SqlCommand();
            cmd.Connection = con;
            cmd.CommandType = CommandType.StoredProcedure;
            cmd.CommandText = "GetSupportHoursByCompanyID";

            //Pass the parameters sent in (companyName, companyLocation) for the SqlQuery
           
            cmd.Parameters.AddWithValue("@CompanyID", "companyID");


            // Execute command
            using (con)
            {
                try
                {
                    con.Open();

                    SqlDataReader reader = cmd.ExecuteReader();
                    while (reader.Read())
                    {
                        Ticket theTicket = new Ticket();


                        theTicket.SupportTimeUsed = (decimal)reader["SupportUsed"];
                       


                        colTickets.Add(theTicket);
                    }




                    reader.Close();
                    con.Close();
                }
                catch (Exception e)
                {
                    throw new Exception(e.Message + " There was a problem getting the support hours used from the Database.");

                }

            }
            return colTickets;

        }



Any insight would be greatly appreciated.

Thanks in Advance.