MC7304 slow in 4G



I upgraded my notebook with a Sierra AirPrime MC7304 card but when I connect in 4G my speed is 2.5Mbyte/sec in download and 8Mbyte/sec in upload, if I connect in 3G speed is 25.5Mbyte/sec in download and 4Mbyte/sec in upload, dunno why

I upgraded my drivers and firmwere and nothing changed

can anyone help me?