Half a million customers of mobile phone firm 3 Ireland face new fees for access to the latest 4G internet service.
The new fees will affect all customers on bill pay and prepay arrangements from the end of this month.
Bill pay customers will be charged an additional €5 per month if they want access to 4G, while prepay customers currently getting 4G will be asked to purchase a monthly 'add-on'.
Those who opt not to pay the additional fees will be stuck on slower 3G services.
The move comes just as 3 Ireland introduces 4G to the bulk of its customers, inherited as part of its O2 Ireland acquisition.
Three quarters of the company's two million customers use what the older O2 network which has not yet been upgraded to 4G. However, the operator is set to switch 4G on this over the coming weeks.
"From 1st July 2015, an additional €4.99 monthly charge will apply for access to 4G for all Bill Pay customers," said a statement on 3's website.
"From 1st July 2015, prepay customers will be required to purchase an add-on in order to attain access to 4G."
It is the latest in a series of price rises from 3 Ireland, which is trying to make it into the black after losing €1bn in the Irish market.
The operator is also understood to be considering a change to its blanket 'all you can eat' data allowances to try and cash in on O2 customers who may be willing to pay more. It comes after 3 Ireland raised monthly phone bills by 25pc to bill-pay customers on 'sim-only' deals. The monthly rise went from €20.33 to €25.41
A spokesman at the time said that price rises were required to meet its running costs.
3 Ireland is now the second biggest mobile provider in the country. It has a 32pc market share with market leader Vodafone on 39pc.
Two new mobile operators are due to begin services later this year, with The Carphone Warehouse launching this summer and UPC launching in the autumn. Earlier this week, An Post relaunched its mobile operator as Postmobile.