Do calls and texts still work?
Does any other data/internet access work?
If not then check the internet settings APN field and if it has changed from 48months.liffeytelecom.com to something else then change it back to that, save the changes, switch airplane mode on and then off and see if data starts working again.
If you still have problems then maybe look at this thread:
https://community.48.ie/t5/Internet/How-to-fix-no-network-service-when-roaming/m-p/56352/highlight/t...
Hope this helps.
