Receiving invoices and statements for an account which is due for deletion

We pay our Irish Water bills for our two houses always in time. A third account exists which was created in error. 

We contacted Irish Water re. deletion of this account by post, email and telephone many times starting in April 2015 and finally we received an email that we should disregard any correspondence regarding this account and that this duplicate account will be deleted from the system in due course. That was in July.

In the meantime we received one more invoice in October. We again sent an email that this account needs to be deleted, we received no answer.

Last week we received a letter for our OVERDUE ACCOUNT, we again sent an email and received so far no answer and to be honest, we don't think we will ever get one.

We are going abroad for a while and we are afraid, that we will miss new invoices, statements, overdue accounts, legal letters etc in the meantime and might be punished for something which we shouldn't be charged for in the first place.

Can someone please help? Thank you.