I had some issues with my dongle due to a change of carrier and probably change of frequency.
My lovely dongle stopped working on 3G network and decided to connect only on 2G, which made my life a hell.
After few head scratches ( 4 hours ), I tried to upgrade the firmware, which was very hard to find due to the old hardware and only few people providing the software.
I found this russian website which has a good archive of firmware, just use google translate to read what the website say.
The procedure is easy:
1) Connect your dongle to a windows machine
2) Run the upgrade firmware software and it will make the device become a serial port
3) If you dont have the driver installed, you will need to download the Mobile Partner software which includes all drivers
4) If you run windows 10, make sure you reboot on "disable signature drivers" or you will never install them
5) You might need to edit the ini to allow the driver to be installed as not all of the devices are listed but the driver is generic
6) After all of this, run again the upgrade firmware software
7) At some point you will be asked to insert a password, go on here and use your IMEI to get your password
8) After all of this, the job is done! I got back my 3G connection.
Small tip, you will probably need to flash WebUI as well, on my case, it just didnt work and I had to flash it.
I hope this helped someone else.