I think Discount Tire is the best example I have ever seen of taking care of in-store customers and telephone customers at the same time. As soon as you walk in, you are greeted, even if they can't help you right away. Every time an employee walks inside from the bay, he looks at the line of customers, makes eye contact, and says, "We'll be right with you."
This model has been wildly successful for DT. Other stores would be smart to emulate it.
Last shop I worked at was like that, or if they were busy at the counter they would pick up the phones and start putting people on hold.