Here in Norway when they broke my suitcase last year they sent me to their authorized partner in town (a luggage shop) that could examine the suitcase and determine if it could be repaired or needed be be replaced. If it could be repaired, they would have repaired it for me and KLM would pay for it. Since it could not be repaired, they valued my old suitcase and allow me to select (for free) any suitcase of that similar cost in their shop or opt for a more expensive one only paying the difference. That is what I did. For me it was a good experience, but I dealt with it as soon as I saw my suitcase came in the belt with a giant hole, prior to leaving the luggage arrival area so it was a real human that saw the suitcase, not a picture. Maybe if I had tried to ask for it afterwards they would have given me some problems.

Are you sure the shop is only supposed to give you the certificate, and not also potentially a new suitcase? (or a repair)