Non signed credit agreement and the company taking money from my account

[menmeryiset]

I signed up for a home learning course and agreed online for the company to take the deposit but did not sign a credit agreement allowing them to take out the installments.
They have now started to take payments for the installments out of my account. i wrote to them to cancel my course as my financial circumstances have changed, but they are refusing to cancel the course and say they are still going to continue debiting my account for the payments.
Can they legally do this despite me not signing the credit agreement? Is there anyway I can stop the payments coming out via my debit card?
Thanks in advance for any help

[ummmm]

You can cancel it via your bank. They might still chase you for the money though.

[menmeryiset]

It's a rolling card debit unfortunately, so it looks like I can't cancel it without cancelling my card :o(

[bednobs]

if it s a continuos paymaent authority, even cancelling your card wont work