As the saying goes: "cash is king." So for limited period, say 4 months, all referrals automatically add Available Funds at $5/referral of any 90 day plan. All other Rewards continue as normal. These Available Funds carry over until fully utilized.
During the offer period, current customers may order 5 SIMs at a time for $5.
Also, consider doing a deal with Orchard to allow Available Funds to be used for the purchase of their phones.