NCO is a collection agency. Many people believe the do not call registry covers collection agencies.... It doesn't, they are calling because you either have an account in collections or you have a phone number that was once registered to someone that they have in their system.
Another one of NCO's collection numbers, presumably on behalf of Credit One Bank. How many numbers does one company need? Just leave a message, we all get how terrible we are for not being able to pay our bills on time. Badgering people into obligations with harassment and repeated hang-up calls causes them to resent you as an organization and tarnishes your reputation as a legitimate business.
They call every hour on the hour. I didn't answer and they don't leave a message. I called the number back and heard an automated voice say "Welcome to Credit One Bank". I hung up. We don't have any business through Credit One Bank and don't know why they are calling.