Comment 23 for bug 1424791

Found following solution working on OTA-12:

Within Terminal:
/usr/share/ofono/scripts
./test-network-registration /ril_0 default

Switches back to hsdpa if available without disconnection from the network.

Testing with
ping 8.8.8.8

If there is no reply the network manager service hangs, then following solves the problem
sudo service network-manager restart