When was it working ok for you last?
What changed in the meantime?
Phone software update, settings changes, phone factory reset/restore, returned from roaming abroad, etc.?
Are calls and texts working ok?
Do you have a connection to the 48 network - i.e. signal bars?
Do you have an active membership plan with a non-zero data balance?
Are your APN settings configured correctly?
Text "APN" to 50048 and follow the instructions here to ensure that they are:
If you need to contact 48 support about this then see the links in my signature below.
