Telecoms company eir has said around 25% of its customers will be impacted by price hikes from August.
The changes in fees will impact households and small to medium sized businesses using the company's landline, broadband, TV and mobile services.
eir said current customers will see a €5 increase to their bills per month.
"eir consistently reviews all plans to ensure it remains competitive whilst continuing its significant investment programme," it said in a statement.
It said all customers are being notified in writing and those impacted will have the option to opt-out of their contract at no additional charge.
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In addition to these changes, the company said it will transition to an annual automated price increase mechanism from next April.
It said this would be at a rate of the consumer price index as defined in January of that year plus an additional 3%, for both current and new customers, in line with industry practice both in Ireland and the UK.
"This annual automated increase is being applied to assist with increased operating costs, supporting further investment, while removing the ambiguity of price increases for customers and ensuring price corresponds with inflation rates," it said in a statement.