You could use your iPhone, as a wireless WAN source as instructed here.
However, the increase in speed is conditional. Load balancing in Teltonika devices is performed on a connection basis rather than bonding, meaning that every single connection is established through a single WAN interface. This speed increase in this case is only possible if:
- you have multiple downloads;
- your download is spread across multiple streams.
In other cases, load balancing simply provides additional resources for more connections, but does not increase speed.