I don't think you can get free subsidy code for this model.. but you can get affordable code from Mobile-unlocker.com
Get the unique unlock code for your phone and the unlocking instructions from the Sony-Ericsson website.
You can get an unlock code for your Sony Ericsson K850i mobile phone from Mobile-unlocker.com .
Motorola i930 IMEI - 356254005231058
If you want to unlock your Sony Ericsson mobile phone from the network lock,I would suggest you to get an unlock code from Classicunlocking.com at reasonable price.
UK
You can get the unlock code for Sony Ericsson K550i from Simpleunlocking.com by specifying the country and network to which the mobile is locked to.Once you get the unlock code you can follow free unlock instructions from Mobileunlockguide.com and remove the network lock easily.
If you want to unlock Sony Ericsson Z750 mobile phone from the network lock,I would suggest you to get an unlock code from Superunlockcodes.com at reasonable price.
If you want to unlock Sony Ericsson Z525 mobile phone from the network lock,I would suggest you to get an unlock code from Unlocking4u.com at reasonable price.
If you want to unlock your Sony Ericsson T700 mobile phone fom the network lock,I would suggest you to get an unlock code from Unlocking4u.com at reasonable price.
If you want to unlock Sony Ericsson W350 mobile phone from the network lock,I would suggest you to get an unlock code from Superunlockcodes.com at reasonable price.
You can purchase subsidy codes from any commercial vendors online like Mobile-unlocker.com
You can get the subsidy code for Motorola V8 from Mobileunlocksolutions.com where you just have to submit your IMEI number,country and network to them.. Further by the instruction they provide you yourself can unlock it step by step...