I don't know what happened, maybe a phone update at some point, but for about the past week Cortana has said she can't connect to the internet when I'm away from home/work. I have a Lumia 920, and mostly use wifi so not that big a deal. I finally thought to check around in System Settings-access point, and found that all the apn and mms settings were blank. I had saved screen settings from when I first set up Net10 so I just re-did the old ones.
Internet apn (not sure it matters but I used no caps on anything)
APN: tfdata
User name : net10
mms apn
APN : tfdata
User name : net10
password : - (blank)
WAP gateway (URL) : proxy.mnvo.tracfone.com
WAP gateway port : 80
MMSC (URL) :
http://mmsc.cingular.com/
MMSC port : 80
It's confusing that everyone seems to be using different settings, but this is what's working for me. I just popped in a Net10 sim to try it on my 920. Someone at a Microsoft Store helped me find these settings, I don't know where they got them (mmsc cingular???) whatever works I guess.
I've been happy with Net10, but actually considering giving MetroPCS a try. $40/month for 1gb data