Dial-up Connection Error 777 – The connection attempt failed because the modem (or other connecting device) on the remote computer is out of order
Dial-up connection error 777 is caused when modem is not connected or configured properly.
With cellular modems, when the SIM card is not present or locked, dial-up error 777 can happen. Use AT Command Tester tool to check the status of the SIM Card.
Module , M2M , GPRS , 3G , through AT commands,