you have to download new main and fs and custpack
you can flash you phone to w800
than you follow this tutorial, and use the main you flashed in patch generator

but i have found you a patch that should work

here it is:

Code:
;K750 SW-R1CA021
;Remove SIM-Lock
;(c) IronMaster
;(p) jasiek
+44020000
b4594c: 70B5041C24F2B2FB00230022011C1C20 F0B505213A22D1F7AFFE0020F0BDC046

;locale=Russian_Russia.1251