He smiles and nods often in sympathy and he replies in a soothing voice.
By smiling and nodding often, he is showing that he is listening to the customers concerns and cares about what they have to say.
By replying in a soothing voice, he is more likely to pacify the customer and make them less angry over not receiving a refund.
These two actions show his interpersonal skills through how he is able to react in a way that is considered polite and more likely to allow him to have a civil conversation with the customer.