Purchased Add removal Plants vs Zombies does not work

To be honest, the original Plant vs Zombie is an old game, this removing ads feature had been working originally but I guess with so many updates for so many new gaming devices and operating systems, something might have escaped the play-test or checking by the QA team (if there is still one doing this task).

Depending on where you are, some countries do have laws protecting their consumers, should a purchase item is found to be unfit for purpose or not as described, you can cancel or reject that item and ask for your money back. 

I would suggest try asking for a refund from the credit card company.

Just for your information, if you do not want to see ads popping up, there are a few ways, the easiest one is just simply turn of your WiFi and internet data or set your device to flight mode.