Trouble Syncing contacts - Keeps replacing names

each time i symc my iphone to itunes, some of the contacts change names or add surnames that i do not want. is there a way to stop this happening so that the names remain the same each time? At the moment, after each syncing I have to go in to both my contacts on my macbook & iphone and amend them individually.

 

Ive fixed them in both address book on the mac & on the iphone at different times. they keep defaulting back to the surnames on my friend's email addresses, which is not what i use on my contacts list. my address book on the mac keeps amending itself. how can i stop this?