Originally Posted by
Often1
Are you suggesting that the law firm is a "fake" law firm?
How else would the law firm have become involved in the matter. I would definitely do a web search and make sure that the firm and the individual exist and then call that individual lawyer. That is who Sixt has briefed to resolve or litigate this matter.
They may well just be a debt recovery firm dressed up to look like a law firm. That is not uncommon in Europe.