What makes a human voice agreeable is a matter of scientific discussion. Whereas prosody was shown to play a role regarding “male-female” attraction, the impact of frequency modulations in “non-sexual”, notably commercial, contexts has attracted little attention. Another point unaddressed in the literature is auditory sensitivity to short-term frequency modulations as current studies focus more on sentence. Thirty French female operators were recorded over the phone. All “bonjour” greeting words were classified in terms of frequency modulation linearity and orientation at the syllable and word levels. Then, the different voices were played back to students and seniors who had to rate each voice according to their degree of agreeableness. Listeners preferred non-monotonous voices. Differences between age-classes were greater than between sex-classes. Results suggest that short-term frequency changes are important for auditory evaluation of voice agreeableness. This study opens new research perspectives concerning the importance of prosody during consumer-seller interactions.