This is a hot potato, basically you are paying for a service, you may have chosen to fly with a particular airline because of what they advertised, even though the small print may exclude them from liability it would be very unfair not to compensate.

Importantly you should always complain as soon as you are aware you have a problem, they may be able to fix it or find you another seat.
If they can not make sure they are aware of your displeasure, be polite but firm, discreetly note the names of all flight crew you deal with, follow up later in the flight by enquiring about the complaints procedure.

Then follow up with a written complaint asking for compensation based on you not getting the services advertised.