CC may be canceled after it has been requested. The method by which this is accomplished differs based on the type of agent the calling party uses.
When using a generic agent, the dialplan application CallRequestCancel is used to cancel CC. When using a native monitor, the method by which CC is cancelled depends on the protocol used. Likely, this will be done using a button on a phone.
Keep in mind that if CC is cancelled, it cannot be un-cancelled.