You are not alone in experiencing this bug. Here is a link to my post in case you would like to read more about this issue: Comprehensive Thread Of All Top 500/Competitive Bugs. I’ve compiled a list of posts regarding similar bugs under: Incorrect End Of Season Competitive Rank And Rewards (Seasons 1-3). Please help in spreading the word about this megathread and other related threads, we must demand the Developers to give us the rewards we rightfully earned.