Along with a letter reminding us all about the referral discount, and maybe a brochure of the plan options and promotions, and an activation/porting guide that we can all give to a friend with the sim card.
Super cheap way to get new activations. Your happy customers are your best source of free advertising.
In a month, you could track which of those sim cards had been activated on new numbers and then either from that data, or the data you get from the numbers entered in the 'who referred you' field, you could send out more free sim cards to all those who actually referred someone.
