Hi, Free unlocking is not possible for your phone model. but you can get the accurate unlock code for a Sony Ericsson C903 from www.classicunlocking.com/sony-ericsson-c903/rs16wp9/
at low cost.
======================================UNLOCKING STEPS FOR SONY ERICSSON C903======================================
1 - Switch ON your Sony Ericsson C903 without
any SIM Card,
2 - Press the left arrow
3 - Press the button * twice
4 - Press the left arrow
5 - The message "Personalize with MNC2" will appear, (or you will have
displayed an unlock menu, select the lock you want to unlock)
6 - Enter the Unlock Code.
If your Sony Ericsson C903 does not have a left arrow button/key(e.g.
Sony Ericsson W950i) and on a few phones(not all) that have a "JOGDIAL"
you must press the "down arrow" key/button instead of the "left arrow"
key/button for step 2 & 4. We mean by "Down Arrow" to direct the
Jogdial down! In the Sony Ericsson W950i and some other models, the down
arrow button/key would be located on the side of the phone.