From the email I received:
Christmas is around the corner and we’ve got a special offer for existing SpinTel customers and their friends. When you order a new mobile service online from Monday 22nd December to Sunday 4th January, we’ll waive the $25 postage and SIM card charge. Simply enter the promotion code ‘spintelxmas’. Signing up to one of SpinTel’s Flexible Mobile plans is a great Christmas gift idea as you’re not locked into any contracts.
Also, use these referrals (or PM me!) for $10 credit (for signing up for mobile services)
https://www.ozbargain.com.au/wiki/spintel_referral_links
Just had a look at the details. Their concept of "bumping" confuses me… If there are no additional cost, why would anyone sign up for anything greater than the "S" plan?