Disabling a "lost" Ademco keyfob?

["brianc33" <brianc@xxxxxxxx>]

I have a residential system monitored by a big national company.  I
just had my worn-out wireless keyfob replaced and the tech took the old
one with him (I should have said it was lost).  I noticed on the
paperwork he assigned all new zones for my new keyfob, and apparently
*didn't* disable the zones assigned to the old one.  So now I have to
assume he left with a largely functioning keyfob to my system.  On the
off chance that he's crooked, any suggestions on how to secure my
system against that keyfob?

Thanks.

Brian G.
San Francisco