Caller: NSW SES

NSW SES, I called back, they tried to transfer me through to whoever called me, got put to voice mail.. never called back

It's NSW SES - State Emergency Service, which means they are on duty 247.

Caller: NSW SES 132 500

From NSW SES at 132500 - Whilst waiting in queue, you get the option to leave your phone number, for your call to be returned. This is during busy periods. You will get a return call from this phone number (02) 4240 3666. Probably best to answer, as its in relation to your query.

Someone from this number called very late Saturday afternoon, meaning it's very unlikely to be a government agency or any kind of 'official' organisation. I let it go to voicemail. Whoever it was didn't leave a message.

It was 3am...My phone is on silent till 6.30am
.

I called back number (02) 4240 3666 spoke to a woman who said I've reached NSW Emergency Services.