Irish Water is insisting that the company is contacting people about their bills in the "appropriate" way.
It emerged yesterday that the utility has begun phoning customers about outstanding payments.
However, management has flatly denied threatening customers with a loss of supply.
Spokesperson Elizabeth Arnett said that everything Irish Water is doing is above board.
"It's important that everybody is paying their bill, and this is the first step in ensuring that happens," she said.
"And this is being done for the right reasons and in the right way.
"The Regulator, the Commission for Energy Regulation, sets out how we can communicate with people, when we can communicate with people, and we are adhering to all of those guidelines etc. and doing this in the appropriate way."