Hi Bisma32,
Since WhatsApp is a free app, it appears as if someone else's Apple ID was used to install it on the phone. Unfortunately, you may have to delete WhatsApp and reinstall it on the phone using your Apple ID. otherwise, you can ask whoever installed it to sign in and they should be able to update it for you. (If you can't remember who then unfortunately you may just have to delete it).
I hope this helps.
-Percival876