Flexiclub wants to sue a dead man

My father in law was a member of Flexiclub. He passed away during July last year. At the time I send an email to them with his death certificate asking them what should be done to cancel. This was ignored, as was the numerous requests to cancel even before he passed because he was simply unable to go on holiday as he was in a wheelchair and very ill. We got the usual story of the request that needed to go to the board (seems as if this board never meets). During September/October Flexiclub tried to deduct annual fees from his bank account which was frozen because of his passing. They are now threatening to sue him for this monies and that they will blacklist him and that his credit record will be affected negatively. I'm not sure how they plan to sue a dead man. Maybe they can advise on this.