It was back in the 70s. IIRC I had a full Y fare ticket SYD-LHR via AP (cost AUD801 - I remember that). On the journey I suspected that the TA had overcharged me (I'd paid AUD960), so I went into the NZ office in Suva (Fiji) to verify it. They confirmed that I had been overcharged and arranged an MCO to cover the refund.

Later in the journey I cashed it in at the NZ office in LA

Long, long ago - can't remember more than that