I was looking for a coupon code and found "25save" for Vodafone, and it is for first month, that will reduce $25 in first month…
vodafone gives 50% off from their first month bill,, so when you apply coupon code (25save) its $0 for first month… unlimited calls/ sms and 300 minutes for international calls
Postage free
Please note that even though this is month to month plan (sim only) they will do a credit check
10% ongoing discount for existing customers thanks to comment by Unity1
i believe code should be 25SAVE