SIM swap is done in seconds - I had one last week and as soon as the new SIM was on the handset it just worked (had to get a new SIM because the old one didn't work on a newer phone model).

UPDATE:  Vodafone store staff did SIM swap for me in about 3 minutes, even though the old number was originally a TelstraClear issue.

They did have a laugh at my pre-Vodafone/non-smart mobile (Nokia 2730 from 2010) <bg>. Still, they broke out a new SIM, stuck it in my old phone, called technical provisioning and asked for a SIM number swap …. said it would take 5 minutes to activate, but by the time the young lady copied my contacts to the new SIM, removed it and placed it in the new phone, it was already ringing as a test call.

Excellent service with a smile .... can't ask for better than that