Memebership

So I went to the Gym company to inquire about their membership,I let my details including my bank details as recommend that as soon as I was approved they will certainly call me or send me a text message,so they were not sure if I could be approved or not because of the type of bank account I was using. They told me I should expect their call within 3days if not a week,mind you that was back in November 2019,since then I didn't hear anything from them,So recently I've been receiving texts messages informing me that I owe them money,my question is since they have my bank details why didn't they try to debt from there?? Well its simple my bank account was declined but how did I have the membership that I dnt even knw about???