Can't find the edit button!
The carrier bundles are found under /var/mobile/Library/Carrier Bundles so you find the one for your network, copy the file carrier.plist then paste it inside the unknown carrier folder overwriting the one thats in there. Might be a good idea to back it up incase you want to go back to original. You should then find that all the apn details are filled in correctly and any missing fields in my case visual voicemail are there also. I also found it best to activate facetime first in the phone settings before doing this as mine was stuck on waiting for activation. Hope this saves you the agro I went through getting it to work