I'm sure it's been asked repeatedly, but...  How to go about the verification process with Datecheck, P411 etc without having someone call my office.  It would not be good for me to have something like that happen.

Most of these services keep the call pretty discrete.  If they didn't, they wouldn't get much business.  With P411, for example, they will call your office and say something like "this is Mary Black from XYZ company calling for [insert your name here]."   They will not say they are from P411, Date-Check, or the actual name of the service, it will just be some generic-sounding fictitious company name.   If your receptionist transfers the call to you, the agent from the company will ask you for whatever verification code word you gave them when you signed up and that will do it.  If they get your voicemail, they'll leave a discrete voice mail with a number to call them back at to do the verification.