Are you talking about this offer on the banner on our Prepaid Buy A Phone page?
Recharge offer: Available to new handset customers recharging on Epic Data Plan $30 and above. Must activate and recharge included SIM. 2nd and 3rd recharges of same value added on days 28 and 56. Recharge within 30 days of activation. Offer ends 31/3/20, unless extended.
If so, you get the bonus credit when you recharge with the SIM you activated it with.