Delta is interesting in that yes, you do enter your number and PIN if you know it, if not you get connected to an operator. Of course this might just be a test of sorts, because what elite level frequent flyer would forget his ff number and PIN (except for Emmett_s of course)?

But, note that they actually have three numbers, plain old SkyMiles number, Silver Medallion, then Special Member Services, which is for Gold and Platinum.