Ok, here goes.
Might or might not work with your model of modem.
0. Backup your ****, and make a small prayer
1. Insert your modem, let it detect the modem and run the software (mobile partner?) as per normal.Once it is running, and you can see your modem signal strength on the program, exit the program (not minimise). Double check in your notification bar that it is indeed not running.
2. Go to device manager and check that there is a serial port that you can connect to:
View attachment 116790 In this case, it is COM4 .Sometimes you can check the port under modems in device manager
3. Download or use a serial terminal like putty :
http://the.earth.li/~sgtatham/putty/0.63/x86/putty.exe . Run it, and connect to the serial port
4. I would suggest to switch the echo on in putty :
View attachment 116794
5. Type in the com port here :
View attachment 116792 and click Open
6. A black terminal window will open. Type in ati and press enter . It will provide you with manufacturer information regarding the modem
7. Type in at^cvoice=? .

It will query whether the voice is enabled on the modem. 1 means voice disabled, 0 means enabled
8. Set the voice to enabled by typing at^cvoice=0 .

If it gives an "error" then your firmware might be locked or that function is not available for your modem. If it says "ok" then you should be ok to continue to the next step.
9. Download a fully enabled version of mobile partner, and install it. e.g.
https://www.dc-unlocker.com/downloads/get/LihV26NW . Do not replace your other software, as it may be needed for the drivers for your modem. Rather, select a different folder to install in if you think there will be a conflict.
10. Run the mobile partner software. USSD commands and voice are enabled.
Good luck