I do sort of an "answering service" for one of my clients that has an extreme hatred of VM and doesn't want his clients to have to deal with it either...I charge $150/month and only have to answer his phones when he forwards them...it seems cheap, but it is not a lot of time over all and he is on retainer with me for other stuff anyway. He always provides a schedule of meetings and gives me plenty of notice...
I think for the chat option, you could charge more...depending on the website traffic.

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Tamara
www.desertdivassistant.com