If you install the same Huawei Mobile Partner, but from different carriers, then one application will be replaced by the other one. Here is a trick to have both apps installed. Go to the Control Panel, then select the Users section and create a username with Administrator access. Afterwards install one dongle and its software using the normal account, and then for the second dongle, keep Shift pressed and right click the installer. Choose Run as different user and select or input the details for the second one you've created earlier.
You'll have two apps of the same kind installed on the same PC. To use the second one, select the Run as different user every time is started.