This is a great question! There are many ways to deal with the phone call however, each scenario is different.
We are trained to answer the phone by the third ring and most times we do. But, this is the quandary begins I am sure.
I think it is all about the customer whom is front of you at the time and whom is on the phone.
You have to read the customer in front of you and see if that person is being impatient. It is imperative that you take care of that customer as they are captive in your store and ready to spend money so you can ill afford for them to walk away.
However, over the years, many companies have put a grand emphasis on the phone-in customer and your company has a policy I am sure. But, in reality that policy is suggestive, right?
So, finally to the answer as I see it. Politely ask the in-store customer to excuse you while you answer the phone. The customer on the phone should be informed you are with another customer and you will be back with them shortly. If you are going to be delayed and there is no one else to assist them you might ask for a number to call them back.
Most customers that frequent our stores know what we deal with and are patient with that scenario. However, if they decide to hold be sure and go back about every 45 seconds or so and let them know you have not forgotten about them.
We also play favorites as well, a customer that spends $2,500 a month with us will get top billing and get helped before the customer at the counter.
Hope I helped with the quandary, thanks for the question.