heres the think though.. they can
by linking your bank account you are giving them permission to pull funds from your account.
you have to check their terms for what they deem as reasons they will pull funds from your account
EG some companies say they want to charge you a monthly fee or a retainer amount or a upfront reserve. you ned to read the terms for what they say they will do if you use their service
lets give you some other real life examples
heck even just parking your car on a rectangle space of tarmac for longer than the land owner allows, gets your vehicle towed away and debt collectors chasing you. and thats without even having to sign up to any membership. thats just being on someones property means you agree to their terms of use
much like many websites 'by continuing to visit this site you agree with its cookie policy and the sites terms and conditions'
.you see facebook, microsoft outlook, and paypal update there terms, they dont even have to get you to 'accept' them no more, they simply state by continuing to use their service you are agreeing to the updated terms. meaning they dont even have to get you to read and accept you have read the updated terms.
this is why whenever using any service, read the terms and if you dont like it, dont use the service.
heck you even see utility companies. like cell phone deals that set you up with a contract. which meant to be a fixed rate zero change policy for the contract period, now can change their rates/policies mid contract where they dont even have to get you to sign up again. they can just start taking more money out of your account or any amount they say the bill is owed.