download and install http://www.rcom.co.in/Rcom/personal/internet/zip/ZTE_AC2726_linux.zip
Then connect and wait for this to appear in NetworkManager
or
Install Wvdial.

edit /etc/wvdial.conf to
-----
[Dialer Orange]
Init1 = ATZ
Init2 = ATQ0 V1 E1 S0=0 &C1 &D2 +FCLASS=0
Stupid Mode = 1
Modem = /dev/ttyUSB0
Phone = #777
Idle Seconds = 900
Password = *your pin*
Modem Type = USB Modem
Compuserve = 0
Baud = 921600
#Auto DNS = 1
#DNS1= 8.8.8.8
#DNS2= 8.8.4.4
Dial Command = ATDT
Ask Password = 0
ISDN = 0
#Auto Reconnect= 1
Username = *your number*
--------

Then run wvdial Orange as root