Once you purchase the ad-free version, you will need to download it from the store on your device. This is because the ad-free and ad-supported versions are different applications.
For this reason, you may still be using the version with advertisement. To avoid any confusion, we recommend that once you download of the ad-free version, you delete the free version of the game.
Please keep in mind the purchase will be stored in your device's Play Store/App Store account. In case you are using another device and do not have the same store account, you will not be able to retrieve this version.
If you purchased the ad-free version and are still seeing ads, we suggest you visit the article: I purchased the ad-free version, why am I still seeing ads?