c330 band change ok, but can't make a call

[Bomber]

i've many c330 with 1900 Mhz band, i've made a band change flex, now phone get network, but signal is very weak and refuses to make a call


is there any hardware modification to get them working correctly

i've found on this forum a solution, rx filter must be changed in order to get phone fully working,

can some one explain me where is it located exactly on mainboard ?


thx