Do you mean that you don't even have a connection to the 48 network - i.e. no signal bars?
If that's the case then what happens if you do a manual search for networks?
Can you see and connect to 48?
If not then try reseating the SIM in case it got dislodged.
What do you mean by "defaulted"?
Did anything change with your phone before things stopped working?
New phone, factory reset, software update, settings changes, returned from roaming abroad, etc.?
If you can't get a network connection at all then you may need to try a replacement SIM:
If you need to contact 48 support about this then see the links in my signature below.
