I'm trying to help a friend of mine. He was supposed to travel from Berlin to Amsterdam with Easyjet along with 3 other people. At the time of boarding, my friend and one of his companions (along with other people) weren't allowed to board because there was no more place in the plane, apparently the plane was smaller than what was sold, his friends did fly. They didn't offer a flight for the same day so he was forced to flight with another airline that he paid. Now they don't want to refund because in their system it says there's no registry of board denial and he's marked as a no-show so terms don't apply. How can he prove or make them pay a refund?
As proof your friend could sure use his friends/companions/colleagues eyewitness accounts of his denied boarding, plus his printed boarding pass and transportation tickets to the airport, even though as @chx points out, this may not be convincing them enough. Also worth enquiring with the airport if they have any records that they are able to share in a court case, but I would not expect much from that.
As a strategy I would go for a combination of these steps,
- insisting on his claims via customer service
- insisting via social media, especially facebook & twitter
- after step 1 fails, ask for a conciliation by the Schlichtungsstelle
if even the last step fails (it takes a while but I have made excellent experiences), I would threaten and go for legal action. Plenty of lawyers have specialized on similar claims and their willingness to take up the case is a good indication of your chances of success.
Also if what you say is true, your friend would have right to EU compensation payments.
You can't prove it, at best -- I do not know how Berlin has this -- you might have a record of passing through security if the boarding pass was scanned. But even so, it'd be very hard to prove your friend haven't passed the time drinking in the bar and became a no show. If you go for a full blown court trial then witnesses might help of course but otherwise...
If his boarding pass was scanned as everyone else's during boarding at the gate then it should be a slam dunk and the airport should have a record for sure but I suspect that wasn't the case.
It's not clear from your question whether you did that already or not but the first thing to do is probably to send a letter (preferably by registered mail) to lay out your claim to reimbursement and compensation, citing EU regulation 261/2004. Interaction on the phone or what you may have been told at the airport carries less weight.
Best case scenario, the fact that you appear to know your rights might convince them it's easier to get rid of you by paying a few hundred euros. Worse case scenario, you have something a little stronger than your word to buttress further action (it's not unimpeachable proof of anything of course, but it counts).
See also the EU Air passenger rights page for more details on the regulation and some other actions you might take.
Others have reported getting a good response by turning to social media (as opposed to private communication through emails and phone, which often leads nowhere in my experience).