Ecom Express — Delivery Not Attempted and OFD Lock Status

I am trying from last 3 days but there is absurd response from the ecom express customer service. The delivery guy who is calling has some network issues, voice not audible and he is updating customer not available. I have updated the alternative number, which was not considered for calling in case of any issues.

Now, after 3 days they are updating OFD lock. Customer care daily refusing to lodge complaint and telling to call after 8 pm.

Now, what is OFD lock and i am not sure if the package will be returned without any attempt to delivery.

Hopefully to get some proper response here.

Thanks,
Nidhi