I'd like to offer coupons/discounts to existing customers. They're on recurrent billing plans. How can I do this? I understand entering a coupon code at signup but what if they've been customers for a while already? Also, if they go to 'renew' and complete that, will they start getting billed twice?
I am afraid it is not possible to alter billing terms in case of PayPal (PayPal handle recurring billings on its own and just notify aMember about new payments). User can only cancel his current subscripiton and then signup again with coupon.