How to receive bigger photo resolution via Faceboo

问题:

I've built a Facebook messenger chatbot and I want to receive photos from my users. When a user sends a photo via Messenger from the desktop, the chatbot received the image with the original resolution. The problem appears when the user sends the photo from the Messenger mobile app. There the received photo has a maximum width/height of 480px

Here's the received photo: https://scontent-ort2-1.xx.fbcdn.net/v/t34.0-12/28233061_10156017194129795_1233684255_n.jpg?_nc_ad=z-m&_nc_cid=0&oh=dafb539de30026d4e86bd5fa30087de6&oe=5A8D4E5A

Here's the return I get:

{"object":"page","entry":
    [{"id":"200900296634090","time":1519039409741,"messaging":
        [{"sender":
         {"id":"1424128924364939"},"recipient":
         {"id":"200900296634090"},"timestamp":1519039409066,"message":
         {"mid":"mid.$cAAC2t6H-60hn3xMzqlhrc3m3_rOn","seq":139592,"attachments":
             [{"type":"image","payload":
             {"url":"https:\/\/scontent-ort2-1.xx.fbcdn.net\/v\/t34.0-12\/28233061_10156017194129795_1233684255_n.jpg?_nc_ad=z-m&_nc_cid=0&oh=dafb539de30026d4e86bd5fa30087de6&oe=5A8D4E5A"}}]}}]}]}

I've looked everywhere and couldn't find any solution.