Greetings manji_patel,
We understand you're wishing to change your device Auto-lock functions and that option is missing. We're happy to investigate further.
As you mention that your device is managed by your company and that is the most common reason for seeing changes to settings, have you attempted to remove that profile if allowed? That would be the fastest way to verify if this is indeed the cause for that behavior, as auto-locking a device increases security by ensuring a passcode or other verification is required to access the device, and you should consult with your employer before making this type of change. If you have an Exchange email account set up, this policy could also be enabled through that account.
We hope this helps!