Once a change event is real, it gets priced. The priced version is often called a potential change order (PCO); when it is submitted to the owner for approval it may be called a change order request (COR). Names vary by company and contract, but the path is the same: price it, send it, negotiate, sign.
The executed change order (CO) is the signed modification to the contract, adjusting the contract sum, the contract time or both. AIA's form for this is the G701. Until it is signed, the work is exposure, not contract value, and it generally should not be billed as if it were approved.
Sometimes the owner needs the work done before the price is agreed. A construction change directive (CCD) (AIA G714) directs the change while the price or time is still being settled. Work under a CCD can typically be billed under the contract's terms for it, but the final number is still open.
Two habits pay for themselves: ask for a time extension in the same request as the money (adding days later is hard), and keep every PCO in one log with status, amount requested, amount approved and the related RFI or event.