Lock your doors and walk away. Put your key in a small tin with the lid on. Take it to the car and see if you can unlock the door. If you can't then you've successfully blocked the signal, so a thief's relay wont work.
Just been told that "remote climate control" is now a chargeable extra on my wifes MY19 Leaf Nconnecta so will be going to small claims court to recover 10 years of charges as it was in the original contract. App is so rubbish compared to my Tesla M3 one.