I'm being harrassed by Irish Water collections for money I don't owe

Hello

I'm getting regular threatening phone calls from Irish Water collections relating to an outstanding bill that I don't owe.

The specifics of the account are that I rent a commercial unit that shares a water line with 6 apartments overhead. The allowance for these residential units was not applied to the account and so our minimal usage (2 person staff using only a toilet and sink Monday - Friday, no other water usage at all) was receiving bills for the whole building.

Someone from water services came out and confirmed that the line is shared and that the allowance should have been applied. Irish Water applied the discount to historical bills that they charged directly, but did not apply it to the bills they inherited from Dublin City Council.

As such I continue to get phone calls and letters demanding payment, threatening disconnection, legal action etc. I get a phone call every 3-4 months, which takes a half hour of me explaining the history on the account and why I don't actually owe the money they're claiming I owe.

Each time the caller promises that they'll log the information on the account, or escalate it, or get someone to look into it etc. However none of that happens and instead I get another phone call from someone threatening disconnection, legal action etc unless I pay.

I even have a copy of a phone call recording (obtained through GDPR data request) where they're admitting that I shouldn't be charged. Yet I continue to be hounded on this.

Today's phone call was from an individual who was particularly aggressive and threatening over the phone and I'm sick of it now, I've told them before that it's getting to the point of harassment and I feel it's crossed that line now.

It's clearly not going to stop and my account is just sitting in the 'collections' pile. Looking for advice on how I can get this resolved.

Thanks