While rare, this does happen from time to time.  It is up to Your Company as to how to proceed.  We suggest:


o Check to see if a new booking can be made for the same dates/room type/etc.  If so, we suggest booking on behalf of the customer, and simply updating them that their reservation number has changed (i.e. send them a new voucher).


If a new booking is not possible, identify some similar options and present these to the customer when informing them of the fact that their earlier booking wasn’t possible to fulfill.