User does not have permission (403) in mobile network

I installed the WD MyCloud very easily and install the app on an android phone.
I can reach my cloud in my local wi-fi and outside in any wi-fi network.
Unfortunately, when I change to mobile data, the app shows me error 403 “User does not have permission”.

I had followed all the steps on this guide ([HOW-TO]: Troubleshooting Remote Connectivity Issues) in order to solve my problem.
I tried to change to static IP, manually configure port forwarding, and nothing happened.
I turned back and put everything as the original definitions. Nothing happened again.

Finally I realized that the problem was on the smartphone. “Definitions” → “Mobile networks” → “Access point (APN)” → Changed the access point.

Now it works like a charm!!