[otrs] Tickets on Hold

Hi, I've been looking at replacing our current Helpdesk application with OTRS but the only thing that I cannot see how to do is put a ticket on hold. What I mean when I say put a ticket on hold is if the customer is unavailable (on holiday, etc) or if parts are on order. Obviously if the customer is away and is unavailable to confirm if the ticket is completed our helpdesk might exceed the agreed SLA for that ticket when it is maybe not the fault of the helpdesk technician. Is this option available in OTRS or have I just missed it? Is there any alternative ways to do this? Thanks Nathan Nathan Gaydon Technical Support Specialist Aeroflex Intl Ltd D: (+44)1438 772046 M: (+44)7743862019