The Man
Unbanned zombie poster
Back in my days of support, in that situation I'd wait ten minutes then email them back with some question about their issue, note in the ticket that the customer couldn't be reached to provide this vital information necessary to proceed, and change the ticket status to "pending customer response".
Just make sure it is a question that hasn't already been answered or the information already provided. The last IT person who tried such a delaying tactic, a few times, on an issue I had would always reference information already provided. So I'd chat back with something like "Information already provided" and screen captures of the chat message with the information, "Only issue still pending on ticket XYQZ is IT support action."