Confirming it's a phone extension in a call center run by Airportlink M7. I got a call from this number and they left me a voice message saying to call 1300 113 330, which is Airportlink M7's main contact number. They were contacting me because my mostly disused account had been sitting at negative $3 balance for some time :P

I called back number (07) 3635 4300 rang 4 times then goes to busy tone.

When I return call to this number the person asks me to please say the name of the person I am calling

I have but won't answer so no clue who it is.

I had the same thing - it is Airport Link M7