So when you said "device password" you mean the password used to login to BIS.
90 days is roughly 3 months, its been 5 months since you got your blackberry. why its taken a bit longer, im not sure, but regardless, its asking you to do it.
I believe it should have come through as a PIN message from blackberry. Are you currently connected to data?
Have you checked the MESSAGES folder?
"That's it then. Cancel the kitchen scraps for lepers and orphans, no more merciful beheadings... and call off Christmas."