I suppose you’re talking about USB speed. EC25 supports USB 2.0 max, so if it connects at USB 1.1 speed, then something is probably wrong with the host drivers.
- USB 1.1/Full-Speed : 12 Mbps.
- USB 2.0/Hi-Speed : 480 Mbps.
Then if you want to achieve higher speeds (assuming radio network allows that at the given location), you should use QMI protocol between the modem and the host, not PPP.
Before comparing results with the phone make sure your phone is of the same LTE category - EC25 is CAT4 device.