I tried to call back the number (02) 9136 2553 but the person who picked up the phone disconnected the call

I returned a call from (02) 9136 2553 but the voicemail didn't mention the company name

I've received numerous calls from this number. It is not a number I'm familiar with, and the caller never leaves a message. If you try to return a call to this number it simply states "extension 9595 is unavailable, please leave a message after the sound then hang up or press the pound key".