Address changes in quote form

Address changes in quote form

When entering a quote, the first piece of information required is the Account, which properly populates the billing and shipping address fields.  Then I use the lookup function to select a contact, and when I do, the billing and shipping addresses are overwritten with, typically blank data.  How do I stop this nonsense?  Did we setup the mapping process incorrectly?  The billing and shipping address in the quote form should ALWAYS be the Account data, not Contact data.

Thanks for helping me find a solution.