Marking a booking as no show in error

I have marked the wrong booking as a no show - can this be reversed?  I had a no show and through bleary eyes at midnight marked the wrong booking as a no show!  What should I do?  I have contacted customer services but no response as yet.  Is there something simple I can do my end to rectify this.  I have marked the correct one as a no show now but just want to sort out the error!