Homebond are usually only for structural issues and notoriously difficult to get even a returned phone call from.
I suggest you call the managing agent immediately about it and make sure you get a name. Then follow it up in writing by email/post, quoting the details and mentioning who you spoke to.
If nothing happens in a very short timescale (couple of working days), get back on to them, and follow up with the directors of your management company.
Have you called up to your neighbour about it? They may not be aware of the problem. Note if the fault is due to their negligence inside their own place, the management company may be within their rights not to help.