Rain internet service provider is a ****

I'm utterly disgusted by rain internet service provider. I canceled the wifi internet in July 2025. They provided me with a reference number but every month they keep on sending an invoice that I owe them the service they never provided. Worse, on daily basis there is is a daily penalty fee that my bank charges for insufficient funds due to rain trying to make a debit funds from my account. I've been communicating with the cancelation department to sort this out since July. They just give reference number for cancelation but on daily basis I keep on getting messages to pay for the internet they never provided. I want all my money that is debited as penalty cause by this ****ty internet service provider called rain unlimited