Answer phone. Fix whatever problem caller has, regardless of complexity, instantaneously. During the instant you're fixing the problem, be cheerful and friendly, but not overly so, while being sure to give the impression you're taking the problem seriously and reassuring the caller their problem is your top (or better yet, only) priority.
That about covers it.
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"Gratitude makes sense of our past, brings peace for today, and creates a vision for tomorrow." - Melody Beattie