You may try connecting from the command line. First create a new mobile broadband connection. To do so:-
- Connect your modem. Then select 'New Mobile Broadband connection...' from the panel(aka menu bar) as shown below.
- Then in the following window press continue.
- Then select your country.
- In the subsequent window select your ISP.
- Then press 'Continue' and then 'Apply'.
Now open the terminal with Ctrl+Alt+t . Then type the following command :-
An output similar(not exactly) to the one below will be shown :-
NAME UUID TYPE TIMESTAMP-REAL
Wired connection 1 ef7249c9-13bf-4d4c-9d5e-14c79371be9e 802-3-ethernet Monday 21 April 2014 11:23:20 AM IST
BSNL/CellOne New GPRS/3G a1f89d7a-12d0-4ef8-b76d-cb6e31b11697 gsm Monday 21 April 2014 03:22:39 PM IST
As you can see the output displays all the connections that you have created. Now in the above case if I have to connect with 'BSNL/CellOne New GPRS/3G' then I will type the following command:-
nmcli connection up uuid a1f89d7a-12d0-4ef8-b76d-cb6e31b11697
As you can see I have typed the UUID of the connection that I want to connect to. So according to your connection you have got to give the UUID in the above command.