We booked this hotel for 2 nights. The first night, despite setting the A/C to 18C, it would never cool the room below 24.5C and, in fact, stopped working.
When we contacted the front desk, they dismissively told us to wait for 2 hours. I calmly and patiently explained that we had set it 4 hours prior, and the temperature had not come down since then. They sent a technician, who explained - possibly erroneously - that you could only have a delta/difference in temperature of 2 degrees between the room temperature and desired temperature. So we set the thermostat to 23C - two hours later, the temperature was still 24.5.
We continued to apprise the front desk of the problem. In response, the front desk agent would sigh, groan, and cut us off when we were explaining what was going on. I have been to literally hundreds of hotels around the world, and have never once experienced such a lack of professionalism.
We calmly stated that it was not unreasonable to expect air conditioning to work, especially when it was very warm outside (over 30C). When they promised to send up a technician a second time, and didn't (after waiting over 2 hours), we decided to move to another hotel in Brussels (Thon Hotel Stephanie) - we experienced absolutely none of the thermostat or rudeness issues there.
We contacted Hotels.com to seek a refund since we didn't spend our second night there. The answer from the hotel was silence.