What are consultants selling?

Time.

Consultants are selling their expertise and knowledge acquired over the years. They are trading their time for money.

Expect to reward the consultant for spending time with you, even if it is over the phone.

If you respect your time, then you should respect the consultant's time also, because the consultant is selling his/her TIME to you in exchange for monetary or non-monetary compensations.

Look at it this way, if every client asks for 5 minutes of free time from the consultant, how is the consultant ever going to find the time to earn their keep?

Most consulting firms have a retainer (business support / or coverplan) program in place. You should consider enrolling in the retainer program so that you can have phone and/or on-site contact with the consultant on any issues you face.