After finishing season 3 of competitive play with Platinum, I was not given rewards for it.
He writes to me that I graduated with platinum 3 when I entered, but no awards were issued. My teammates were given these awards, they were indicated on the menu where the rank is written.
You are not alone in experiencing this bug. 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.