Please advise as to what to do as money has been taken from my account despite my cancelling my subscription at the start of this month.

For starters, you can e-mail the devs with the account info and your problem, since right now, no one knows who the hell you are, and I'm guessing the devs will have a hard time trying to fix the problem like that.

Definitely, you should contact support team and they will cancel your subscription without any problems.