Alter price after booking is confirmed, applied discount. How does guest get refund?

[Barry-And-Gail0]

I took a booking which was accepted and confirmed by a guest.  I had forgotten to setup the weekly discounts.  So I set them up and advertised the weekly discounts in my description.  The guest saw this and asked if it applied to his booking.  Which I did by altering the booking and manually changing the price.  How does he get the refund.

[Fred13]

IF you mean the new price was set to apply to everyone else, I do not think their price can be changed, since it was 'set' for them upon acceptance of their particular booking. Unless their booking is 'Altered', which they then have to accept at their end to become effective.