I recently have a 22 kg parcel to be sent from Onehunga to Auckland central.

Really I want to find a same day service.

But I entered up at nzpost.co.nz, signed up an account.

"My NZ Post Business"
After I enter the both addresses, it shows only overnight option available under Courier

This is what I am confused about:
What's the difference between NZ Post, NZ Post's "Courier", CourierPost and New Zealand Couriers.

I know DHL, FedEx are completely different companies, but these four above use similar colours and terms.

Anyone know?