You can remove a charge off by disputing it. This has to be done directly with the credit bureaus.
A dispute is your way of saying this mark is not accurate or not valid. There are two ways to file a dispute.
1. Write a dispute letter
This is done yourself. In this letter you simply identify the charged off mark and provide a reason for its inaccuracy. Reasons can include; not my account, account paid in full, item is out of date.