When a cargo has been connected to a Contract of Affreightment (CoA), a secondary action called 'Remove CoA' will be enabled which will allow you to revert the connection and disconnect the cargo from the CoA. If the Cargo does not have any CoAs connected, the Remove CoA button will be greyed out and disabled. The Secondary Action menu is opened by clicking the triple-dot icon in the upper right of the Cargo Drawer
Clicking the 'Remove CoA' button will instantly disconnect the CoA link from the Cargo.