If you dont have service on those, switching probably wont help much. At least that is currently my experience.
oh yeah wet, Ive been using that 12121 and it drove me nuts. when I switch to channel 650 area(which is actual 3g for me) it would lose data because i was "roaming".
It was kind of fun because it actually put me onto roaming channel/sid (950/86 verizon) and something like (580/1055 blue? wireless). When I' try to make calls it would put me through to a recording from those companies the blue wireless told me to dial 611, the ctmod menu would say roaming, Id get the little triangle up top and a warning message saying "You have lost data connectivity because you are roaming".
Which would be awesome if I could use it, I actually wouldnt mind no data for increased service.