The first 11 digits represents my number. This is what is showing on text message once this unknown call come thru and I could not even block coz there is no number showing on 'missed calls' but on voicemail I hear people chatting on the background for few seconds. These calls are mostly done during 8am onwards for a few seconds. Even if I try to engage and take the call, no one speaks. So, bottomline they are doing this just to annoy people.