MIssed a call from this number.

I started getting these calls after putting my cell number into Paypal for an alternate way to restore access if I lost my password. Thanks for nothing, Paypal "security"! They never leave a message. So far, these are the numbers that show up as the "caller":
469-620-0220 on 5/21 and 5/19
386-213-8715 on 5/21
304-362-5973 on 5/19
573-342-3609 on 5/18
312-883-7697 on 5/15
281-545-0325 on 5/15
224-704-0495 on 5/14
312-878-3759 on 5/14
512-580-4255 on 5/12
210-627-8613 on 5/11

Robot girl said "hello" and something else but I hung up at hello.

Definitely some sort of scam, I answered and no one was on the other end. I called back the number as I thought it may have been a client who was disconnected. The on thing on the other line was an automated message saying "all representatives are busy, please press 1 to be added to the do not call list" I didn't press anything at all thinking it would let me hold while a rep got to my call, and then it went on to say that my number was added to a don't call list. I'm worried now that that is going to flag this number as a "working, used" number and just continue to be flooded with calls.

received a call, line was dead