Cannot edit contacts on phone

Whenever i try to add a contact i cant, how do i do this?

Also, when i try to edit a contact i get the error message "Unable to edit SNS contacts on phone"

The only way i can edit or add is to go through gmail online.

PLEASE help me with this. 

Thanks

Thanks for helping, but it still is not working. To add a contact, i hit the menu but i do not get a "add contact" option, not ever under 'more'.

If i try the plus sign next to the search and try to add that, i only get the name, number, and email fields with no option to edit.

If i try to add by typing the number in first and then 'add to contacts' i only get the list of contacts, nowhere to add a new contact.

As i said, the only way it is letting me do it, is to go to gmail and sync which is not helpful if i need to add someone away from email.

I should just be able to add a contact, my sister has the same phone and she has the add option, so i am not sure why i havent??

PS> I have an "my profile" option, is that there instead of 'add contact'? if so, how do i remove it?

I am having a similar problem with my contacts - I only seem to have an option for first name - I have gone into settings for contacts but it does not give me an option for both first and last names. I know I did have the option but it seems to have disappeared - Any ideas?