Telefonica Spain APN Settings for Apple iPhone 7 Plus

From main menu, select Settings and then Cellular.

Check that Cellular Data is turned on.
Tap Cellular Data Options and then Cellular Data Network. 
(If this setting does not appear it cannot be configured manually. Please contact the seller.)

Go to Cellular Data and enter information as below

APN: movistar.es
Username:
Password: MOVISTAR

Go to LTE Setup (Optional) section and enter information as below

APN: (Leave Blank)
Username: (Leave Blank)
Password: (Leave Blank)

Press the Home button to save the APN and exit to the main screen.
Restart the iPhone.