Your post is not that clear.
What is the exact prompt/error/message?
If it's something like "SIM network PIN" then your phone is most likely locked to another network and needs to be unlocked before it can be used on the 48 network.
How do I unlock my phone?
If it's something like "SIM PIN" then you enter your PIN1 and if you don't know that you use your PUK - see here:
I forgot my PIN
Hope this helps.
