I never pick up when I see a number I don't know. Hell I barely pick up when it's someone I do know! I checked the number on the internet and I think it's bill collectors called Firstmark Services. Are they calling anyone else?
Call ID shows WalMart but caller claims to be with a home security system company offering a GE home security system free or at reduced cost if give information and allow posting of their sign in your front yard. The company name was not written down. Call back to the number is an automated answering system with no specific information about the company but gives option to remove your phone number from their call list.