Charged Double for a pro-rata month

I was billed the equivalent of two months for my first month, which should have been pro-rata, mind you. I called when I first picked up on this last year and only until recently when they decided to increase my subscription cost did I see that the ticket from my initial query hadn’t yet been resolved (a year later).

I’m calling again and now the lady is trying to tell me of unrelated charges and how they’re valid, despite me emphasising that I’m referring to the very first charge I received when my pro-rata period ended.