Beste antwoord door Rizana NS
Hi Juliana, welcome to the NS Community.
I am sorry to read you thought you couldn't return the bike in Diemen Zuid. If it was full, there's a possibility to park the bike somewhere near the OV-Fiets rental location. You could hand in the key in the blue dropbox. After you did that, the customer service can make a note in the system you did return the bike (with the exact location).
Because you didn't bring the bike back to the place you rent it, we charge €10.00 extra. You can read about this on our website. Hopefully all of this is clear for you now.