It is frustrating...
As stated before, you might need to try Freedom mobile Sim or Roaming mobility SIM card to change setting.
Here is another thread on this issue:
Heres the breakdown of my experience.
1. Asus support - three different times contacting them, first guy I told him he was dumb, second was helpful gave me a case number, third, case number was useless and so was he.
2. Public mobile forum - helpful with the knowledge you have
3. Original seller, sent me a new rom, problem fixed!
Why is Asus so useless and could not have given me a new rom?