There is no single published number because it changes contently depending on the nature of the call and agent availability. Following the link below will either give a current number for you to call or take your number for a callback.
(Note that phone support is for paying customers only. There is no phone support for Free Customers.)
Here is a TurboTax FAQ for contacting customer support.
**Disclaimer: This post is for discussion purposes only and is NOT tax advice. The author takes no responsibility for the accuracy of any information in this post.**