Hello,
The simplest way to find out would be to enable a packet capture for your WAN interface to monitor data flows.
For that, download TCPdump package from Services -> Package manager section. Once the package is installed, navigate to System -> Administration -> Troubleshoot section. Enable TCP dump for wwan0 interface, save the settings and leave the device for some time to simply monitor data. Download the TCP dump file after some time, analyze it with Wireshark, or attach it by editing your question to check for moderators.
Best regards,
