[AT&T Samsung Galaxy Note II] k2trf:
When you flashed your custom ROM, you may have nuked your APN settings!

As the title says, I think your problem may be related to custom ROMs wiping out APN settings that may have come from the store (or put in by Net10 upon activation/initialization of the phone), and if that's the case, I think I can help you!

I've just gotten done activating (read: porting), configuring, flashing with custom ROMs, and setting up APN settings on 4 unlocked phones that we brought to Net10 (on AT&T's network, via the BYOP program, since these are unlocked GSM/WCDMA phones), I believe I can assist you here.

Rather than trying random combinations of APN settings to try and find one that works, if you call Net10 Customer Support (877-836-2368), all you have to do (once you tell them your phone number/SIM serial number) is ask for someone who can assist you in updating the APN settings for unlocked phones.

You'll be transfered to a different section of Net10's/Tracfone's Technical Support, and whoever picks up will likely tell you they can assist you once you repeat what it is you need help with. They'll tell you the usuals (make sure WiFi, Bluetooth, and Airplane Mode are off, and make sure Cellular Data is enabled, but not Cellular Roaming Data), and then they'll tell you to go down into your SIM/Mobile Network settings screen, and create a New APN. They'll read off the settings they should have, and they they will (or if they don't, you should ask them to "resend the switch and update the settings on their end" in those _exact_ terms, as they've cut the times for this from 3 hours to less than 30 minutes per phone for me).

Then they'll tell you to select the new APN settings, and reboot the phone (or turn it off and back on if your ROM doesn't have a reboot option); they'll have you attempt to open a browser and pull a page down (I highly suggest a mobile site of some sort, being that they're the lightest; it'll either work here or not, there is no "to what degree does it work"). If it doesn't work, they'll give you different settings (though it's not taken more than two APN setting tries for me, and that's mainly because of the area I live in), and then try the browser again. Once the browser is able to pull a mobile site, they'll ask you to try sending a picture message (again, I reccommend a small picture, as it either works or doesn't, so the size will only hold you up longer the bigger it is), even if it's just to yourself.

I've found that if you're simply respectful and paitent with them (as they sometimes have to spend 10 minutes putting various bits of data into other spots on their computers), they will be able to get it done for you within half an hour per phone.

I would highly reccommend that you don't mention your custom ROM however; so long as it doesn't interfere with the APN settings they will never know any better when you tell them you just have a "Samsung Galaxy Note II", and they'll be none the wiser as they fix it for you (because it realistically makes no difference in a problem like this).

If you mention it however, they won't want to help, because they don't know anything about custom ROMs (it seems they're all very terrified of them, and believe they are the spawn of Pewdiepie and Justain Beiber or something similar! XD)

Hoping I've been able to help you here, since I've extremely recent knowledge/experiences to do with the APN settings myself! (Also post whoring as I apparently need 10 before I can let the developers of my custom ROM know about some bugs I've found, go figure!)

If I'm incorrect on the issue, then I'm terribly sorry, and please feel free to ignore me -- I do not claim to be affialiated with Net10, Samsung, whatever ROM you have/whoever wrote/maintains it, etc., and am only trying to be helpful where your problem sounds like something I've dealt with before. :)

EDIT: I just realized I left out the most important bit! The entire reason for calling them instead of working through all the various permutations of APN setting combos is because your APN settings will be based on [A] your SIM, your phone (NOT ROM, just the phone's IMEI pairing to the SIMs), and [C] your home area/location you use the phone most often.