I answered the call, but there was silence for a while, so I just hung up. I guess I didn't wait long enough?

I answered, "Hello?" And no reply. I hung up.

I called back and they said, "To be removed from our phone list, press 1 now." I just hung up.

Offered low interest credit cards in the voice mail. Female voice. Can't tell if recording or real person

This is a software generated VOIP call that can not be traced to the crook who is attempting to find someone stupid enough to fall for the bait of a "new low interest rate credit card."  A computer determines if you answer the phone, and then the call is directed to a con-artist who starts with the lies and scam.

They do not have to comply with the "Do Not Call Registry" because they are thieves.

If the unsuspecting idiot answers the call and says "Yes, I would like a new credit card..." that's when the crook starts asking for personal information in order to engage in the act of IDENTITY THEFT. And minutes after the person provides their personal information, typically the physical address, a work address, an account number, driver's license number, full name, date of birth... THEY GET ROBBED.

Lesson here is DO NOT ANSWER ANY CALL FROM AN AREA CODE YOU DO NOT RECOGNIZE. IT'S ONLY A CROOK CALLING.

its actually not a crook its the CIM through US ARMY attempting to leverage a calling pool of anonymous routers (basically a proxy) so that the CIA can harass people or get them rated as terrorists to check their databases - when the US ARMY started using it they were actively trying to enlist and aid and recruit a CULT by leveraging PLAYBOY assets through hugh hefner's son to try to build up communes and political motiffs and register brain scans and neural activity to drive everyone into nudist colonies or get them out of their houses to purchase the houses for military extricates (blacklisted military service members who are apparently accidentally listed as black ops because they are actually black listed and not actual black ops) - though, it still goes right back to george bush senior because he IS that guy