Mobile users hit by border roaming
Some border mobile phone users in Northern Ireland have paid around £300 in additional roaming charges a year, an Ofcom report said.
In the worst affected area of South Armagh and South Down almost a third of people experienced inadvertent roaming on a daily basis.
The problem occurs when a consumer unwittingly or unavoidably makes or receives a call or text message or accesses the internet on their phone on a network on the other side of the border.
Ofcom Northern Ireland director Jonathan Rose said: "While the European Commission has lowered the maximum roaming rates that operators can charge, our research shows that the problem of inadvertent roaming continues to be costly for tens of thousands of consumers in Northern Ireland."
In South Armagh and South Down 30% of consumers encountered the problem every day but the problem was less prevalent in East Derry and North Antrim.
The latest European roaming regulation places a responsibility on mobile operators to take reasonable steps to protect their customers from inadvertent roaming charges and Ofcom said it would write to operators to find out what actions they plan to meet the new obligation.
Lower price caps, introduced on July 1 by the European Union, further reduced roaming charges for voice calls and text. The rules also saw the introduction of a cap on data roaming charges for the first time.
These will reduce the unit price of using roaming services and potentially lower the cost of inadvertent roaming, however the overall cost to consumers may not decrease as usage continues to increase.