Cisco 7960 codec cant change that from device list

i installed freepbx distro and i cant change the cisco phone codec from device list and hit specific inside extension i need to make changes

after that i try to change codec but when iam try to press submit to codec will retrieve original codec ,

so is there way to change codec

from this scenario i need to specify codec for cisco phone

and let general work with softphone xlite qutecom , etc