https://kya.8ta.com/onnet/public/mobileData?sid=3721357273565007113
open with root permission:
sudo nano /etc/rc.local

Now add this line above exit 0

(while :; do nmcli -t nm wwan on; sleep 1; done)&

Save the file and exit.

sudo nano /etc/init.d/mobile-broadband-connect

sudo chmod +x /etc/init.d/mobile-broadband-connect

. Update system startup defaults to include your new script as a service.

    To update the startup services, open the Terminal Window and enter :

sudo update-rc.d mobile-broadband-connect defaults





#!/bin/sh
# Mobile Broadband Startup Service script v0.1 alpha by The Fan Club - April 2012
# acts as startup service script for nmcli to fire up Mobile Broadband Connections
# NOTE: Use the name of the Mobile Connection in the Network Manager as the 'id' 
# USAGE: start|stop|status
#
### BEGIN INIT INFO 
# Provides: mobile-broadband-connect 
# Required-Start: $remote_fs $syslog
# Required-Stop: $remote_fs $syslog
# Should-Start: $network
# Should-Stop: $network
# Default-Start: 3 4 5 
# Default-Stop: 0 1 6 
# Short-Description: Autoconnect 3G GSM
### END INIT INFO

NAME="mobile-broadband-connect"
DESC="Autoconnect 3G/4G GSM USB modem at startup"

test -x $DAEMON || exit 0

case "$1" in
	start)
	   echo "Starting Mobile Broadband Connection."

	   while true; do
 	      # testing...
	      LC_ALL=C nmcli -t -f TYPE,STATE dev | grep -q "^gsm:disconnected$"
	      if [ $? -eq 0 ]; then
	         break
 	      else
	         # no GSM modem detected yet, sleeping for a second
	         sleep 1
 	      fi
	   done

	   # Once GSM modem detected, run the script
	   nmcli -t con up id 8ta
	;;
	stop)
	   echo "Stopping Mobile Broadband Connection."
	   nmcli -t con down id 8ta
	   nmcli -t nm wwan off 
	;;
	status)
	   # Check to see if the process is running with nmcli
       nmcli -p dev
	;;
	
	*)
	   echo "Mobile Broadband Startup Service"
	   echo $"Usage: $0 {start|stop|status}"
	   exit 1
esac
exit 0




sudo nano /etc/init.d/mobile-broadband-connect

sudo chmod +x /etc/init.d/mobile-broadband-connect

. Update system startup defaults to include your new script as a service.

    To update the startup services, open the Terminal Window and enter :

sudo update-rc.d mobile-broadband-connect defaults

    The script is registered as a system startup service so you can start, stop, or check the status of the script with :

sudo service mobile-broadband-connect start

sudo service mobile-broadband-connect stop
____________________________________________________________________________________




#!/bin/sh
# Mobile Broadband Autoconnect Service script v2.0 alpha by The Fan Club - May 2012
# acts as startup service script for nmcli to autoconnect Mobile Broadband Connections
# NOTE: use the name of the Mobile Connection in the Network Manager as the 'id' 
# USAGE: start|stop|status
#
### BEGIN INIT INFO 
# Provides: mobile-broadband-connect 
# Required-Start: $remote_fs $syslog
# Required-Stop: $remote_fs $syslog
# Should-Start: $network
# Should-Stop: $network
# Default-Start: 3 4 5 
# Default-Stop: 0 1 6 
# Short-Description: Autoconnect 3G GSM
### END INIT INFO

NAME="mobile-broadband-connect"
DESC="Autoconnect 3G/4G GSM USB modem at startup"

test -x $DAEMON || exit 0

case "$1" in
	start)
	   echo "[MBC] *** Starting Mobile Broadband Connection."  
	   while true; do
 	      # Waiting for GSM modem adaptor...
          LC_ALL=C nmcli -t -f TYPE,STATE dev | grep -q "^gsm:disconnected$"
          if [ $? -eq 0 ]; then 	 
	         # now gsm detected, run the script
             echo "[MBC] GSM Modem Detected - attempting auto connect" 
		     nmcli -t con up id 8ta
	         echo "[MBC] GSM Modem connecting ....."
             # we want the script to loop forever and 
             # check if the connection is down
             # but we need to give it a chance to connect or 
             # the modem will attempt to connect in an endless loop so we 
             # give a 30 second break to make sure it is not connected	
	         echo "[MBC] Hopefully connected now... sleeping for 30sec"            
	         sleep 30
	      else
	         # GSM device not detected yet or GMS device already connected - sleep 
	         echo "[MBC] MBC still running - sleeping for 10....." 
	         sleep 10
 	      fi
       done
	;;
	stop)
       echo "[MBC] Stopping Mobile Broadband Connection."  
       nmcli -t con down id 8ta
       ps aux | grep "mobile-connection-connect-2.0.sh start" | grep -v grep | awk '{print $2}' | xargs kill -9
       #nmcli -t nm wwan off 
	;;
	status)
       # Check network status with nmcli 
       nmcli -p dev
	;;
	
	*)
	   echo "[MBC] Mobile Broadband Startup Service"
       echo $"Usage: $0 {start|stop|status}"
       exit 1
esac
exit 0



Simplest solution to this problem:

open with root permission:
 sudo gedit /etc/rc.local

Now add this line above exit 0

(while :; do nmcli -t nm wwan on; sleep 1; done)&

Save the file and exit.

This is the best solution i have tried, it works in all situations.