Unauthorized debi-check requests

2nd attempt from Planet Fitness to activate a monthly debit order for membership, without any signed contract. The first time when I challenged them they produced a signed contract, upon further investigation by a member of staff, this happened after my son enquired about membership. When we asked who consented to the contract they quickly apologized and said it was a misunderstanding. The second attempt they again claimed my son signed, however because he is older than 18 they can not share his signed contract with me. When I asked them how they verified my bank account details against his credentials they become uncooperative saying I have to take it up with him.

This happened about 4 months apart, clearly they are still using the forged document to try and ***** money from unsuspecting people.