Whatss app creates Duplicates in Phone Book

[AC Question]

In my Phone Book, Contacts appear twice. One time with their Phone Number, and a duplicated entry for their Whatsapp Number (which is the same, just with spaces)

When going to

Contacts->Settings->Filter

I unchecked the "All Contacts" Box for Whatsapp. Nontheless the Whatsapp duplicates appear in my Phone Book.

Hope Someone can help me out, thanks in Advance.

(I'm using a Sony Xperia Z5 Compact with 6.0.1)