ibis Bamberg Altstadt in Bamberg

My worst stay in a hotel so far. I decided with my partner to spend a weekend in Bamberg and choose the one in Altstadt as a better choice (there is another Ibis in that town). We checked-in on Saturday and paid the bill as requested by the personnel standing in front of the desk. We had even a nice chat with him. The next day, I was asking for a late check-out (as Silver member I should have it). However Mr. Stanislav T. extended it up to one hour, i.e., 1pm, as according to him there were no availability. But the worst had still to come in terms of hospitality. When we came back after our morning walk, Mr. Stanislav T. called us from the desk and said that we need to pay an extra 30 Eur with explanation that we did not pay for the second guest. This is where I draw the line between being a loyal member of Accor and been blamed by its staff to not have paid the full fee. See, I do not pay for a hospitality service to get blamed by staff on mistakes that they make themselves.
The gentleman who checked us in saw both of us and if there was something missing in our booking he should have pointed that out at that time and things would have been solved. But no, in IBIS Bamber you never know what will come. Each time you pass by the reception desk you can be approached or even called and be blamed for your booking.
Despite my arguments to Mr Stanislav that the escalation he is doing was an error that the hotel had to do with, he kept escalating the situation in front of the lobby - what a hospitality. I kept telling him that he is holding a yellow sticker in his hands showing that the hotel knew that there were two people booked for that room. But no, Mr Stanislav T. become more aggressive, where I said I am going to complain to Accor; He actually threatened me to put me in Accor's "red list" so that I would never be able to book a Accor hotel.
In short, you pay a pricey night for a better service, you perform the payment as asked by the staff following check-in procedures, and what you get back is blame, red-list and hard-feelings.
I will follow this up with Accor and see how they are going to manage this situation. But I won't leave this to sleep. No, no Sir - an apology and a bottle of water that you offered me at the end, which I did not accept, after what you said are not a way on how customers are treated.