private enterprises OIDs don't allow configuration

Cisco EPC3008 modem, SNMP issue: some private enterprises OIDs don't allow configuration from SNMP commands.
Although it must be configurable, in particular:

saCmMtaCliAccessType.0 disable(0)
saCmMtaCliAccessInterface.0
saCmMtaCliAccessUsername.0
saCmMtaCliAccessPassword.0

How it can be configured?
Also, a lot of Broadcom private enterprises OIDs are hidden when snmpwalk.