To clarify, we do offer various forms of assistance during the booking process, and throughout the journey. Some requests can be accessed via qantas.com, while others may need to be actioned by our 24/7 Reservations or Special Handling teams.
However I read the OP to be talking about two different issues (apologies if I misunderstood) – requesting assistance for his mother-in-law (in particular, access to onboard toilets), and forward seat selection.
Seat selection is always subject to availability, and as you know, preferential seating zones exist for Platinum, Gold or Silver Frequent Flyers, equivalent oneworld members and any passenger travelling with those flyers in the same booking.
However, without knowing the level of assistance required, and details such as whether there’s a mobility aid being used, it’s difficult to confirm if all options have been exhausted, or if this could have been better communicated by our customer service agent.
My request for booking details was to ensure that the correct notes have been added, and also so I could follow up with our Reservations team for feedback to the individual who took the call. Alternatively, the OP could call 13 13 13 for further assistance.
Thanks, I've received your PM and will get back to you asap.