The hotel changed the bill to a business package room rate which shows no breakfast charges.
What exactly is the problem then ?
What was the hotel and booking type?
Everything that you have posted has indicated that the final bill had the correct amount on it
EUR13 per person plus tax could come to EUR28 once taxes are added ( if rate displayed was exclusive of tax )
What was the rate quoted before adding breakfast and what did the hotel bill actually show.
I don't understand why you wouldn't have purchased breakfast it at EUR14 per person but would have purchased it at EUR13 per person