The OBi200 has a DND function, but it's not automatic. You would have to dial *78 to enable DND, and *79 to disable it. If you want something automatic, your provider would have to offer this function. GoogleVoice and Callcentric have a DND function based on time of day. If your provider doesn't offer this function, you can forward all calls to a provider that does. GoogleVoice and Callcentric have free accounts. Depending how you forward calls, you are adding 1 or 2 hops to the call plus you're adding another possible point of failure.