Please ensure that you have installed the following packages
* usb-modeswitch-data
* usb-modeswitch

Connect the device and see whether it is detected automatically in the network manager
if not do the following things.
.Open the terminal
sudo nautilus
A new window will be opened for root
.Go to filesystems ----/etc/usb_modeswitch.d
.Create a new config file named 12d1:1505
.Cut and Paste the following
DefaultVendor= 0x12d1 

.Save the file
.Go to terminal
.Go to the path by the code
cd /etc/usb_modeswitch.d
.Type the command
sudo usb_modeswitch -I -W -c 12d1\:1505
.It may connect automatically..
.Just wait for one minute
.The default network manager may detect your device and follow the instructions by it
mark it to connect automatically in the mobile broadband edit options
.If not open your network mannager go to manage connection
open the mobile broadband and add a new connection
if it detects installed CDMA device or Huawei EC156 follow the instruction given by the network manager
mark it to connect automatically in the mobile broadband edit options
.Rebbot your system and see it is connected automatically
.If not you have to type the two codes mentioned above all the times when you connect your device
It will be very diffficult to type the codes all the go for the following steps to run that commands automattically

Script to run the modeswitch command in boot
1.Open the gedit
2.Type the two commands which you want to run in two separate lines. the file with the extension .sh on the disk where ever you want and make this file as executable in the properties
4.Then right click on the desktop
5 Create launcher
6.Set type as Run in terminal
7.Give your desired name
8.Give the path of file with the extension .sh in the command box
9.Hit ok

Open the launcher.....
enter the password if required

You can change your icon in the properties of the new launcher file

Connect your device when ever required and click the new icon on the desktop
Hit the password.....