UNLOCKING VODAFONE MOTOROLA SLVR L7 please help????????

a free or very cheap method preferable that if at a charge - i can pay securely using a solo card.

but prefereably a free method or unlocking code etc

WELL I THINK THIS IS WHAT I NEED

i have a pay as you go vodafone and i want to put an 02 sim in it and when i do and turn it on it asks for a ''subsidy code''

i presume this is becuase the phone is locked?

any answers helpful

10 points for one that works for me asap and cheaply/free

thanks