On a system reinstalling encounter with problem – didn’t work 3G modems’ connect manager. To know rest traffic or account balance have to switching off modem, push SIM card into cell phone and by means of USSD commands to require balance and rest of traffic.
When it bothered write console application which make possible to send USSD commands to 3G modem, in case of malfunction of connect manager or if connect manager don’t support necessary commands.
It works with any 3G modems: ZTE, Huawei...