Just because a suite shows up on the website, does not really mean it is ready for occupancy. There is occupancy status and housekeeping status. A room may be vacant, but not cleaned. The room will still show as available on the websites. Rooms may be dropped from cleaning for any number of reasons on any given day. The Front Desk has no control over that. So, keep that in mind when you are showing that agent your iPhone screen and they are looking at the Tape Chart to see what is actually available for occupancy. Some hotels do not have housekeeping staff 24/7, some have different staffing for daily service/room turnover and nightly turndown (they aren't interchangeable).
Just saying that the Front Desk is not always lying/lazy as many of you seem to think every time you aren't granted an upgrade.