Epic Cards Battle

I'm not one to post bugs usually bit slightly irritated at this one...When I registered I put in a referral code and I hit level 20 but I didn't get a reward from hitting level 20. I don't know if I misread it or if it's a bug...

No, it's not. You get the reward - Diamond Card right away when you are level 1.

What it means is the referrer (player who refers you) will also get rewards when you reach level 20.