If you have a Nest Doorbell the camera will still work but none of it will be recorded nor received on your phone or computer.
A nest doorbell will partially work without a subscription but without the subscription the nest doorbell is no better than your regular doorbell.
Having the nest subscription for the full features of the nest doorbell is well worth the cost for security it provides you with.
You can pay $10.00 per month or $100.00 per year for the nest aware subscription and I highly recommend it as that's not even $1.00 per day.
It cost at most $0.34 cents per day which is totally worth it.