Yes you can! (If your company allows)
You can buy up to 30% of the difference between your current reward points and the cart value. For Ex. If Nemo has 500 Reward Points in his Wallet and he bought an Amazon Gift Card worth 600 Reward Points, then he can buy the extra 100 Reward Points because it is within the limit of 30% buying threshold. Also, with 500 Reward Points in his wallet, Nemo can buy any item/s totaling to 650 BigFish Coins and buy the reminder difference. Anything over and above 30% difference will not be possible for Nemo to buy.
Why can't I buy all my Reward Points?
Because it defeats the whole purpose of this program! The aim of this program is to incentivise you to be more engaged, perform well and exercise the values of your organization, for which you will be appreciated by them and eventually, points will be rewarded to you. So the whole idea is for you to earn reward points, rather than buy reward points.
And don't you think it's more fun and rewarding to earn points. Won't you feel happy when your organization appreciates you and gifts you Reward Points? Food for Thought!