I just received a call from this number today. When I asked to speak to a manager, I was connected with someone named "Theresa". She started making jokes to me asking if I suck dick for money. So I thought it was just a spoof number for a prank phone call, here's where it gets interesting:
I called back the 877 number found here (1-877-503-2115) and said I was an FBI officer investigating. The person willingly complied and gave me a number to the "HQ" which is: 1-888-872-7808
I just called them. The 888 number is IQORs tech desk. They connected me to the consumer advocacy group. I was very rude and hasty to the lady, but she assured me she was adding me to a real do not call list. When I informed her of how IQOR does their business, she said she was unaware and has never received a phone call like this one. I bet.