Contacts

I once again had to check something in my phone and again in my contact list they added some more contacts in my list and I do know these people but I prefer not to have them in my contact list and I then had to stop and delete them and I do not want to get a reply about how to delete contacts as if you read this I know how but I want to know why this keeps happening to me as I was not using the phone as I was on the computer and just in one of my sites playing a game so I sure do not appreciate this happening to my contact list and just leave it alone and if I want to add a contact to my list and I sure do know how to do this also thanks