Flexi use FLX3003 = ~ $14 (Save $6)
Unlimited use UNL3003 = ~ $28 (Save $12)
If you want $10 referral credit on signup, browse previous deals here for a referral link
You can use the $10 credit towards the second month making it $10 for second month of flexi or $30 for second month of unlimited
(If you want to try Amaysim, this way remains cheaper than Kogan and Aldi mobile for the first 2 months + Amaysim don't charge you a SIM or shipping fee)
I purchased five months worth of Unlimited vouchers on my ING card during the last 30% off deal at Coles, which made it $26.53/mo, in addition to 30% off signup and another $50 back through StartHere - effectively $18.43/mo in this first six months. So keep an eye out for another supermarket discount if you're keen on Amaysim.
Kinda regret it in my case as it turned out the Optus network has poor indoor reception in my area compared to Telstra/Vodafone, and Kogan came out with their Telstra-based plans shortly after. Apart from that, I've been pleased with Amaysim - no hassle stackable voucher recharge system and seemingly decent customer service.