This approach worked for my Huawei Fonic Surfstick (with model number E1550):
1. Choose “Network” in System Preferences
2. Choose “HUAWEIMobile-Modem”
3. Choose “More Options…”
4. In tab “Modem” choose “Null Modem” from Manufacturer dropdown menu
5. In tab “PPP” check “Connect via Terminal”
6. Press “OK”
7. Press “Apply Settings”
8. Press “Connect”
9. Enter “atz” and press return in appearing terminal window (you will not see the characters appearing)
10. Enter “atz^u2diag=0” and press return
11. Press “Cancel”
12. Reset HUAWEI modem settings (uncheck “Connect via Terminal” and choose “Apple Modem” from manufacturer dropdown menu)
Happy no Mobile Partner time!