Iphone 3 uploading old address book contacts

Hi, hope anyone can help as I am getting crazy, I was given an Iphone 3G S and all is fine when performing sync from Itunes, the only problem is to update new address book contacts, as it keeps picking up the old data and I do not know where from, as they have been changed in the address book.

I tried to erase them from Iphone and upload it again, same result...

It looks like it keeps using some old data in a back up folder or what.

Thanks for helping.