If you can't get any network connection at all then it's nothing to do with the apn.
If it's an iPhone then see the tip that I linked to earlier.
This is a common problem with iPhones when roaming in some networks due to the stupid way that Apple do things.
If you DO have a network connection and calls/texts work but data does not then check your internet/APN settings and if the apn field has changed from 48months.liffeytelecom.com then change it back to that, reboot and see if data starts working.
If none of that helps then you'll need to contact 48 support.
See the link in my signature below.
Hope this helps.