You mean that you've just joined 48?
Did you successfully activate your SIM?
Is your phone unlocked for use on any network?
Do you have a connection to the 48 network - i.e. signal bars?
If not then what happens if you do a manual search for networks - can you see and connect to 48?
If not then what happens? Any error messages?
What happens when try to make a call?
Any error messages?
Can you send/receive texts and use mobile data?
What make and model of phone is it?
If it's an iPhone then it may need activation on the 48 network due to the convoluted way that Apple do things.
This involves the iPhone silently sending an SMS messages to a UK activation server.
This will fail silently if you don't have cash credit on your account to pay for the UK/international text message.
If this might be the issue then you'll need to put €1 cash credit on your account, switch the phone off and on again, wait a little while, and see if that helps.
If you need to contact 48 support about this then see the links in my signature below.
