Zero Rating for Rain internet service provider

So about + - 4 months ago I cancelled my Rain service as I no longer needed the service provider due to upgrades on another internet service provider. I being an abiding customer followed the protocol to cancel my subscription which I thaught was done. Little did I know they do not update there systems then the calls started telling me I owe them and outstanding subscription which I don’t as they had to refund me because they not supposed to be debiting my account. I then called my bank and explained the situation and they advised me that because Rain is a subscription and not a normal debit they cannot stop the debit orders unless Rain does this as they are the service provider. So being a good citizen I contacted Rain and advised them they need to cancel my detail on their side which they said they did and they refunded me yet again money they were not supposed to be taking from my account I made clear to note that I do not owe them anything and they confirmed I do not owe them anything. I thaught that was it hai I’m still getting calls from Rain telling me I have an ousting amount on my account now you tell me am I not supposed to get frustrated because this is becoming ridiculous a large corporation such as rain have staff that don’t check the notes on the system telling them not to call me as I have no dealing with them any longer. One would of thought it would of been that simple but clearly it is not for Rain. I am disgusted with the harassment and pestering I am receiving from Rain very bad service in my opinion they are the worst organization I have had to deal with thus far. Lack of interest in sorting out complaints all they want is money for a weak service they provide. Zero rating for you Rain.