In my experience NZ call centre agents won’t take over a travel agent fare - have tried to do this before. Typically this is because the fare conditions often vary between NZ and the Travel Agent. We use a corporate travel agent with similar rules on flights of less than 5hrs. Usually I just email my account manager and get the TA to charge my personal CC instead of the company account for the upgrade. Again- in my experience - the only time that a NZ consultant will take over a TA booking is for a reward upgrade or service disruption.