SILENT CALLS WHILE HEARING OTHER PEOPLE IN BACKGRO

I KEEP ON GETTING CALLS FROM +27 84 145. WHEN I RAN OUT OF MY MEETING AND ANSWERED THE PHONE IT WAS A TUNE PLAYING. LATER TODAY I RECIEVED ANOTHER CALL AND I CAN HEAR THE PEOPLE TALKING IN THE BACKGROUND HOWEVER THE INDEVIDUAL THAT CALLED ME CHOSE TO REMAIN QUIT UNTIL I DROP THE LINE. MY PHONE IS A COMPANY PHONE SO I AM OBLIGATED TO ANSWER IRRESPECTIVE WHAT I AM DOING. I DO NOT HAVE TIME FOR GAMES OR PEOPLE THAT CALL ME JUST FOR THEM TO SHOW THEY HAVE CALLED SOMEONE...