yun calls kasi from abroad doesn't have to send the A number. it stays in the central office of origin if charge or in the destination exchange if collect ang call for billing purposes. wiht regards to local calls that doesn't appear sa callid ninyo, may clir feature that is use para di maka call back yun customer in case the csa use their private numbers. some government officials request this for security reasons but only given on a case to case basis kasi ma defeat yun purpose ng callid.