Default How to get rid of the ''unnamed'' contacts once and for all?

Hello!
I have a recurrent problem with Sense, it's saving ''unnamed'' contacts in my phonebook without asking me, now I have about 3000 unnamed contacts in my phonebook!!!
I can delete them one by one but it will take hours.
I tried to put ''unnamed'' in the contacts search to delete them all together but Sense won't see them as they don't have a name!
Any tip?
Also why and from where Sense is saving these contacts??