vauxhall astra 2003 vdo cdr 500 cd plater safe on display?

hi car has just come back from garage and the cd player has got safe displayed on the display, the manual says see maindealer??? could i fix this with the right codes or is it maindealer job?

if i can could someone pass on the correct security codes or other codes and the instructions on how to do this hope to hear from you soon sarah