Misinformed and charged for it

I signed up for fibre with Home-connect during a promotion. The sales agent told me that the promotion is till the end of May however after signing up (2nd April), and only after the fibre was activated (6th April) did they tell me that the promotion is only for 1 month. When contacting them to tell them that thats not what I was told, they refused to rectify the situation and said they would charge me to cancel my services, even though I have not used it and billing has not started, and I was given misinformation. It was a very frustrating incident. I also have WiFi with them for my parents. I cannot wait for the 12 months to end to cancel any services I have with them.