Airtime rewards (cash to card option)

Is there anyone who has redeemed on O2 PAYG and can tell me how it works? Do you know if you redeem for O2 PAYG - whether you get a credit voucher which can be applied to any O2 PAYG phone or is it only applied to the actual number linked to the account? My main phone is Voxi which is not supported, but I have a couple of O2 PAYG classic sims for the priority benefits - can I claim an O2 PAYG redemption and apply it to any O2 PAYG phone? Do you get sent a credit voucher code or do you just get credit onto the specific number specified in the redemption?