Double Billed

My landlord at my old apartment gave me notice late on the 1 Feb letting me know I needed to move out at the end of the month. I cancelled my fibre with HC the next morning and sent them a support ticket explaining the 1 day-late cancellation. I was contacted by someone from HC saying that they can't accept the cancellation for 1 March unless I sign up for HC at my new apartment. Which I did, and she assured me that she would link the cancellation and the new order at the new address and that I would not be double billed. Yet 1 March I am double billed! I queried this via a support ticket and got a response asking what I wanted the refund for even though I gave them details in the support ticket. The support ticket is still open, but no refund or further communication from them.