s6 not upgrading to mashmallow

[usama ali2]

I am using galaxy s6 g920f. When i press update it says you are already updated to leatest version . Kindly guide me how can update my phone and if do it manually i can't find frimware with csc No. Is there any problem if i install frimware with different csc No of same model
Want to upgrade my phone to mashmallow
current version 5.02
Baseband version: G920FXXU1AOBH
Build number: LRX22G.G920FXXM1AOBI
UNITED ARAB EMIRATES
CSC: G920FOJV1AOBH

 

[lucianus_luciferus]

i assume the phone is locked on a network?