CALL CENTRE AGENT PUTS PHONE DOWN ON ME

I was trying to block a ****** phone which was on pay-as-you-go. Used to be on contract. The lady told me I must go find my IMEI number before she can help me. I don't have the box anymore and I do not know how to find the IMEI number any other way. She then said she will help me if I can tell her the exact date and time I started using the phone and the exact time and date I used the phone before it was ******. I mean really, I have 4 different phones I use on a daily basis for different things. How am I suppose to keep track about when and what time I use what phone. Other service providers can pick up what phone my sim card was in and provide me with that phones IMEI number, why can't CELL C? Or should I say why do they not want to help!<br> <br> Can someone maybe please assist me with what else I can do to block this phone and to get an ITC number?