As long as hindi ka pa na-boblock before, changing your APN might work. Pero once na-block and nag-roam trick ka na, detected ka na sa system ng sun. Kaya may possibility pa rin mablock even after changing your APN settings.
Ayaw na sa akin kahit *222# "Not allowed to use the menu" na daw. :( Sayang kaka-register ko lang ng TU and yung balance ko dun pang roam on/off. HAHAHA