Generally, the most telemarketing calls I get are from Citibank. I usually say "No thanks" or hang up on them. However, I won't tell them to put me on a "Do not call" list. Why? Well, one day, they called me with an offer I couldn't refuse.
Caller: "Sir, because you are a preferred cardholder, we'd like to offer you a 3.9% Annual Percentage Rate on your card, which will remain until you pay off your balance." (At the time, I owed them about $3000.)
Syc: "What's the catch?"
Caller: "The only requirement is that you stay current on your account."
Syc: *has never missed a credit card payment in 7 years* "You're serious?"
Caller: "Yes sir."
Syc: "So, all I have to do is pay on time as I normally do and I get this? No fee?"
Caller: "Yes sir."
Syc: "You're not lying, are you?"
Caller: "No sir."
2 years later, I'm a happy man with a 3.9% APR on my account...which does wonders for paying down the balance.