Kogan’s site presented the following page.
The explanation at the bottom re privacy and use of the information is typical of many service providers.
Why Kogan could not respond with a quote, you would expect an explanation. Having to phone them? Did you provide a contact number for them to discuss with you?
It does appear a tactic to get you to enter a potentially higher pressure sales situation, person to person over the phone.
I’ve not followed through with Kogan. I have contacted a number of different retailers re better deals and get the occasional unsolicited call. Typically Energy Australia or Alinta in the past. They are generally all a right royal PITA to deal with. Whether they really need a current phone bill, I doubt it is essential. Although your location and metering details may be relevant, as well as an email to get the offer in writing.
P.S.
There are a number of topics on the regular Choice web site with guidance on finding the best electricity deal.