Hotel Ulmer Stuben in Ulm

I booked a double room for one night. I contacted the hotel and asked them for an early check in, agreeing for the 18 Euro fee. I informed them that I would be arriving in Ulm at 12:00. When I arrived the receptionist collected the fee, but the room was not ready. She went upstairs, leaving me in the lobby for about 10 minutes, and then returned. She gave me the key to room 34. During our interaction, she repeatedly asked me if I wanted to pay for the breakfast buffet for the following morning, I repeatedly told her (four times) that I would be leaving early, and would not be needing breakfast. She was very aggressive. I felt she was just trying to get more money. I went to my room and immediately notices that the floors were wet. I also noticed the room was small. My first thought was, "I wouldn't stay here again." As I was in a hurry to meet friends that I had not seen in over 40 years (I am in my 60s), it did not register to me that the room they put me in was not the room I paid for. They put me in a single room, when I had paid for a double. I wanted a double because I have had lower back surgery and single beds can be uncomfortable for me. As it would turn out - very uncomfortable. I attempted communication after returning later in the evening, but was ignored. As I was laving very early in the morning, and there was no one in reception, I contacted the hotel afterwards to ask for a reimbursement in the costs of the room. They refused. They then proceeded to suggest I had made a booking error. I had not. I am a single traveler in my 60s. They made a mistake (or did it on purpose?) and then refused to correct the problem - all for a few dollars. The lamp was cracked. The fan was broken. The refuse to communicate, and, when someone pays for a room, and is given a lesser room - without compensation, then that is stealing. Stealing from a senior foreign traveler - shame on them.