Problems importing contacts

Problems importing contacts

i am having problems importing contacts: i have tried several times but i only get the error message "could not import due to missing mandatory fields, despite having matched all the fields to the appropriate columns in the sheet..
(just for the record: we have set first name, last name and account name as mandatory fields in the contact module)


i first thought it may be due to the user settings: we have recently downgraded from 2 to 1 user, so i` ve tried both import options just in case:  The import fails as described above when i try to import to "import to my contact list", while it duplicates the contact instead of overwriting when i select "import to my organisation contacts". 

I cant figure out what is going wrong: 
im attaching the excel file below: is there anything wrong with it?