Get calls, no voicemail and how do I stop it?

Got a call from this number with no voicemail.  I have noticed an increase in these types of calls also where they just call and if they get your voicemail they don't leave a message but still call all the time. If you are on the do not call registry, how do you make these calls stop?

Recorded female voice states I am eligible to consolidate my credit card debt, but only for a limited time.
Recording does not identify who it represents, but tells me to press 9 if interested. I pressed "end."

Do not call my cell phone.  I'm on the DO NOT CALL LIST!!!!!!!!!!!!!!!!!!!!!!

Received this call and pressed 9 to see about lowering the interest rate on my credit card.  A lady came on the phone and wanted a bunch of information from me including the last part of my social security number.  I would not give out the information.  If the company had received my information from one of my credit card companies as they said they had, then they should have it already in their system.