I am slowly going to work at making most inquiries from my web site come in via email. I find that the vast majority of people calling (two or three a week) are looking for nothing but free advice and I find it very very difficult to be polite and advise them that we offer consulting for a fee.
Most play the game of asking you 50 questions about how you bill, etc.
This still takes 30 minutes per person to politely walk through.
Very few will end the call with anything more than ""I'll think about it and call you back"".
Most are searching for a second or third bid or to see whether you give them different advice than their current consultant.