Receivables Performance Management "RPM" Bottom Feeder Collection Agency! Do NOT give them any info! Bothell, Washington

Just received a call from this company @ my WORK # looking for my husband. 
The woman who answered the phone couldnt find his information to start with and then proceeded to try to figure out what phone # they called.  I did not volunteer any information; as the phone call was odd to start with.
Asking for payment on an AT&T debt from 2000!!!!! Over $500.00!!!!! 
I told the lady we do not owe anything to At&T and in fact, we have AT&T service currently.
She informed me that maybe I "should check w/my husband and then get back with her'----too funny.
I advised her I pay the bills and we owe nothing to AT&T; not to mention the fact, that even if we did; the debt is from 10 years ago!!
She said that statue of limitations in Indiana is 10 years ( which is incorrect; its 6 years - Im in collections :) and that they will find another phone # to contact me at & hung up.
SERIOUSLY????????
These people should be shut down and ANY idiot who agrees to pay the NONSENSE theyre asking for deserves to be taken for a ride.
They had an out of date BOGUS debt; a 10 yr old address and NO valid contact information.
They may very well be a valid collection agency; but they are obviously bottom feeders who are looking for suckers. BEWARE!!!!!!!!!!!!!!!!!!!