Overbilling and acting against the Consumer Protection Act

I have had my contract with Rain since 2020. It's an uncapped service at the same cost since we got the contract (month-to-month). My invoice description of my plan, even specifies the amount per month in the billing line item. Firstly, I selected a specific date I want to pay, 10 days before payment I get SMS to remind me I can pay earlier, so they have my contact detail. Secondly, this month I want to make payment only to find the subscription has been increased without notification in writing as per the CPA requirements and their own contract states. I phone in asking for the proof that I was notified of the increase, on the 15th May, I am still waiting. So they are charging more on a service. I phone in today and they tell me it's CPI linked increase, meanwhile CPI is 6% this increase is in fact closer to 10% increase. Without notification which is against the Consumer Protection Act. This is unacceptable. We have major connectivity issues, I've asked on numerous occasions for the router to be replaced with multiple tickets opened. I don't know what allows them to think they can act outside the law??? I am very dissatisfied with this service