If you tried to use an aloSIM discount code and received an error message that said 'Unable to use your own code,' that's because your Refer & Earn discount code cannot be used by the account that generates it.

Since the referral code is unique to your account, the system registers that you're the "owner" of that particular code, and it won't let you give yourself a $3 discount. That $3 discount is only available to people who use your code during their very first aloSIM purchase.