Should you wish to contact Hostelworld directly you can find the details of your contact person on any of the email notifications you get from Hostelworld, for example booking notification confirmation email.
Alternatively if you check Your Hostelworld Contact Info tab at the top of your Hostelworld Inbox screen :
We offer a 24/7 service line for property owners and managers and our Head Office number is:
+353 1 4980700
Shanghai Office: +86 21 5228 6000
Sydney Office: +61 2 9993 1035