Domain names

HI
The company I work for had a website built around wordpress on a .org domain.
They then pointed the .com at the site, moat of the site runs on the .com but we have around 15% of our pages/links/posts using the .org(this is according to google).
Whats the safest way to get rid of the .org

My apologies for a newbie question but ive read all official docs and am still ot 100% sure.
thanks