You'll need to provide a bit more info than that...
What country are you travelling in?
What make and model of phone are you using?
Can you get connected to a local network?
Do calls and texts work?
What exactly happens when you try to use data?
Is the APN configured correctly?
In particular is the APN field configured correctly?
Set to 48months.liffeytelecom.com and not anything else?
Hope this helps.
Short answer: If you like to travel, don't use a Mobile Virtual Network Operator (MVNO).
MVNOs in Ireland are 48, GoMo, Tesco, Clear Mobile, An Post, etc,. You're much better off with the main operators, although 3 should be avoided due to awful customer relations issues.
MVNOs have A LOT of problems providing services when roaming. Over the years, myself and the family have tried a variety of handsets, and have been with 48, Tesco, and GoMo. We always have problems roaming, with no mobile network access at all or only partiel functions (e.g. receive calls but not make them). We have engaged with the support communities and network chat many many times, followed all the best practice and recommended settings, to the point that we now know that MVNOs cannot provide reliable roaming services.
I totally agree. I've spent literally hours trying to get data roaming working in Spain with no success. This has been going on for three years with me while on holiday. 48months is great for Ireland but in my experience it is no use for data roaming abroad.
I wish 48months would just own up to this shortcoming instead of wasting people's time.