I put in security code that no other sim card use my cell phone now I have forgotten the code and cannot use any other card in my sony ericsson w300i

You can get unlock codes for your Sony Ericsson w300i at Simpleunlocking .specify your network and country and get the unlock codes from them. This site is reliable and provide simple unlocking steps!!!

yes surely you can unlock your Sony ericsson mobile with codes because there are many methods for unlocking mobile phones in that codes are the best way, it is easy and safely unlock your mobile without any damage , in my experience i am telling you , get the unlock code for your sony ericsson w300i model mobile, through this site www.theunlockarena.com/sony-ericsson-w300i/rs13wp9 , it has the some best instructions and ways for unlocking your mobile .....

First try The default lock code it is 1111
if not You have to use a cable but u could try this Just put a different SIM card i.e. SIM card of a different carrier (Eg: AT&T,Orange etc)
and there will be message saying INCORRECT SIM
just type this code : *#7465625*12*37491037#

and then restart your phone .
if it helps please leave a 4 thumb rating.
thanks.

May be Your Mobile locked to some Network,so that it saying wrong Sim Card,You can get the Unlock code here http://www.mobile-unlocker.com/sony-ericsson-w300i/rs2wp9/
and Unlock the mobile from the Network lock.

Use unlock code to unlock your mobile..Get the unlock code here http://www.mobile-unlocker.com/unlock-your-phone/rs2wp2/ and get the unlock instruction in this site http://www.mobileunlockguide.com/

Just put a different SIM card i.e. SIM card of a different carier (Eg: T-mobile, etc)

and there will be message saying INCORRECT SIM

just type this code : *#7465625*12*37491037#

and then restart your phone .
your phone is now unlocked..~~~!!!
Best of luck

pls insert the old sim card and try to restore the security settings in the the settings the problem will be solved

You must enter Security Mastercode instead of lost/forgotten Security Code or Phone Lock code when phone asks for it.

UR SECURITY MASTER CODE IS 3033216440

press frm joystick write side once then press*then 2times joystik left side then *then again frm write sidepress once u will go into service menu then u can see ur passward. no need of smcard when u do this.reply me

code is default of 00000