A method for locking and unlocking a receptacle for a mobile telecommunications terminal device, such as a smartphone. The receptacle is arranged in a holding device. A token is assigned to the holding device and secured against removal in an insertion opening. The token is released when a telecommunications terminal device is locked in the receptacle. When the token is inserted, an authorisation check is carried out for checking an assignment of the token. If the assignment is confirmed, the lock is unlocked. A signal is thereby generated when locking the telecommunications terminal device in the receptacle or upon successful authorization. The signal is transmitted to a blocking element that blocks the movement of a first control element. The signal activates the blocking element to end the block of the control element movement. There is also described a holding device for a mobile telecommunications terminal device.