Vodacom
Lost phone

I called the Vodacom call center advising them that my Blackberry phone is lost and somebody is using the phone, the consultant that i spoke to advised me that they cannot locate who is using the phone, i asked him that is he saying the the IMEI number is useless he kept me on hold and never came back to me. when i first called Vodacom the lady that i spoke to blacklist the phone advised me that no one will be able to use the BBM pin, but yesterday somebody is using the BBM pin and i was able to chat with that person. now the only thing that i needed was the phone number that the devise is currently using and nobody can assist. am i correc in saying that the IMIE number is a cell phone ID.
all the numbers that i called keeps refering me to the network provider
can somebody take the initiative to assist me with my query
my cellphone information is as follows
IMEI : 355419059327240, BBM Pin 2AEACAE0 Model Blackberry 9320 black, old number 0720931010