Try switching off, taking the SIM out, gently cleaning the contacts, putting it back in, switching on, manually searching for networks and connecting to 48. If that doesn't help then you might need to try a replacement SIM. You might also want to contact 48 support. See the link in my signature below.
Hope this helps.
I am not a 48 employee so if you need to contact 48 support then use option 3 or the chat facility here.