That lady just does not want to do her job. Most of my incalls are for early afternoon so I usually check in in the mornings. I don't even bother calling in to request an early check in. I just go to the hotel of my choice that morning, and ask if there are any rooms available right now. People rarely say no to your face and I have never been turned down or charged extra thus far *knock on wood* Same goes with early check-out, usually you cannot check out same day before midnight. I tell them I can't stay until then and hand them my room card. They say okay and I leave.
Plus sometimes walk-in rates are actually cheaper than paying to pre-book. I have booked for less during a walk in vs. prebooking rates online
And if anybody was wondering, I book 3 star hotels or higher. I particularly like the Marriott chain of hotels and Embassy suites. It's also your demeanor that helps. I am not aggressive and ask with a smile but I walk in like I am on a mission and my tone of voice denotes that even though I am asking for available rooms, you're only response will be if I would like a double or a king suite (always king, floor 3 or above, no connected doors).