In China we always write cell numbers. Always. Otherwise stuff goes missing. Recently a large number of urban single-use electronic lock postbox providers have

In China we always write cell numbers. Always. Otherwise stuff goes missing. Recently a large number of urban single-use electronic lock postbox providers have emerged, which automate away the inevitable phone calls from time-poor couriers and deliverymen by SMS-ing you a code to your local single use postbox. If you go enter the code, you get your mail. Otherwise, after 24 hours or some exceedingly short time they take it away and your parcel enters no mans land, in which case you have to request redelivery.