Unauthorised payment - cancelled upfront

I entered into a free trial period, and cancelled numerously within the free trail period. Yet AVAST still deducted an annual subscription fee, even after accepting my Un subscription. I want a refund immediately. The site is so un user friendly, you keep on going in circle to unsubscribe. When trying to change or delete my card details it was not possible, yet after the deduction it was suddenly possibly?
Truly unprofessional.