Some dude I could barely understand called & said I owed AT&T money. I told him I dont owe anyone a [***] thing. He hung up , I backtracked the number , it was RPM, a collection agency in
Waldorf, MD.

its a collection agency i beleive....they asked who I was..I only said a first name...they asked for my father only by first name...coincidence...maybe.....who does in fact have a many collection accounts with people...they gave me no information kept me on hold..it was like they were just confirming it was his phone number... to actually reach the person though..basically to confirm an identity...then they said hold on and never came back to me...so I hung up after several minutes.

RPM, ReceivablePerf, Receivable Performance Management.  Debt collectors which are bottom feeders as they try to collect past due debts that are well past the statute of limitations.
You can find all you want or need to know about them on their website: www.receivableperformance.com   Their location is in WA.  Their website lists area codes 425 and 503 and they have both 866 and 888 numbers.  I have no idea who they are paying for the 240 area code MD phone number.  No doubt another scum sucker like themselves.
If you are having trouble with them, keep track of the number of times a day they call as only 1 call is allowed whether or not they actually reach you.  Then report them to the WA attorney general's office consumer affairs division.

These people called and asked for someone I don't know who apparently gave my number as a reference. When I said, take my number off, they said that they can't unless I give them my cell number. Then how are they calling me? This is BS and I don't know if they are a scam or what.

I got a call from this number today on May 18, 2010, but I do not have
a balance on any of my credit cards.  Actually, I have been receiving numerous
nuisance phone calls that are from, or connected to, my family and relatives.
This call was a missed call, which I will not return.

If this particular call is from them as well, then we are dealing with  an
organized crime family situation, associated with the Church of Scientology.
They have been harassing me like this for five years continuously, and also
periodically for over 30 years.  In the past, harassment has not been this consistent,
as it has been in these last five years.   Since December 2008, most of this harassment
has stopped, but I must emphasize the word "most".  

Specifically, you are dealing with Seth D. Derish and Seth Derish, Jr. who are also known
together as Derish Associates.  My extended Silver family is associated with them as well.
All of these people engage in various types of financial scamming and drug trafficking.
The Derish Associates also accept and execute murder contracts also.

However, both Seth D. Derish and Seth Derish, Jr. are currently incarcerated in California
on murder charges, and both were not arrested and convicted at the same time.  Seth D. Derish
was arrested about December 10, 2008, and that is when" most" harassment has stopped since
that time.  

Therefore, most people placing comments, here, do not have exactly the same problem as
I have, but we are all dealing with the same people, or people connected to my organized crime
family, which I often refer to as the Derish-Silver crime family.

I am not representing myself as a licensed private investigator, and I
am only acting for my own concerns and interests.  The motives for my
family and Derish  Associates, to harass me, is not entirely clear.  I have
not seen my family in over 30 years, and there has been very little contact
during this time.

All I could suggest to callers, besides advice already given here , is
to file an incident report with your local police department, regarding suspicious
circumstances or nuisance phone calls.  You may naturally use the information
I have provided here, as you wish.

DS Investigations