The phrase 'pick up check' can be replaced with several antonyms, depending on the context. To decline a check or refuse to accept a payment, you could use 'turn down' or 'reject.' To leave a check behind, you could 'abandon' it or 'forget' about it. If you want to delay cashing or depositing a check, you could 'postpone' or 'defer' it. Alternatively, if you wish to relinquish or transfer responsibility for a check, you could 'delegate' or 'assign' it. Regardless of the antonym you choose, be sure to communicate clearly to avoid any misunderstandings or confusion.