If you’re travelling to or living in a border county, your phone may occasionally connect to a roaming network due to proximity to another country. This is called inadvertent roaming and may lead to unexpected roaming charges.

Counties Affected

Donegal
Louth
Monaghan
Leitrim
Cavan

Avoid automatic connection to roaming networks by changing your network settings:

Go to Settings.
Select Network.
Choose Network Selection.
Set it to Manual National.

To avoid inadvertent roaming, you can disable data roaming or turn off mobile data altogether in your phone's settings. Or you can select the network you roam onto, so to avoid the device automatically connecting to any network. Other preventive measures include using Wi-Fi whenever possible, turning off automatic updates:

Disable data roaming and mobile data: In your phone's settings, turn off both "data roaming" and "mobile data" to prevent any international connections.
Turn off automatic updates: Stop your phone from automatically downloading updates and apps by disabling this feature in your settings.
Close unused apps: Shut down apps that might run in the background and use data even when you're not actively using them.
Disable Wi-Fi Assist: Turn off any Wi-Fi Assist or similar features that may automatically switch to mobile data if the Wi-Fi signal is weak. 
Turn off ‘Automatic network selection’: Go to SIM Cards & Mobile Networks: Navigate to the SIM cards and mobile networks section.
Choose the SIM: Select the SIM card you want to change the network for. Access Preferred Network Type: Find and tap on "Preferred network type" or a similar option.
Turn off Automatic Selection: If the automatic network selection is enabled, turn it off. Select Manual Selection.
Select a Network: The phone will then search for available networks.
Choose the desired network from the list.