Technically you could force that situation with a trigger.
However, usually this is something you actually wouldn’t want in case your customer has something else like.
“Oh no important appointment got in, can’t join at 5”.
By default Zammad will notify you on the ticket update by mail and notification - that means you could jump into the ticket, see it’s not relevant and put it back into pending reminder.
If you choose the trigger approach, please keep in mind that “pending till” is never reset.
This means that it’s quite hard to filter for it in a good way.
Right now I have no idea to be honest.