Firms are rapidly adopting social media platforms to optimize their customer service operations. Given the central role of social media as a primary point of contact with customers and the critical importance of maintaining high levels of customer satisfaction, it is imperative to craft positive experiences during service interactions. To enhance customer interaction with a personal touch, U.S. telecom giant T-Mobile replaced standardized profiles with personal profiles for its social media customer service agents on Twitter. Leveraging this exogenous change, we investigate how these personal profiles affect customer behaviors within service operations. We adopt a difference-in-differences empirical strategy in this research. The results show that implementing personal profiles for customer service agents increases positive sentiment in customer tweets, reduces the likelihood of complaints, and improves overall satisfaction. Further analyses suggest that the effects vary across customer groups, with greater impact among verified Twitter users and female customers. While personalized agent profiles can enhance satisfaction, they also heighten expectations for timely responses, making delays more detrimental than with standardized profiles. To explore the underlying mechanism, we conduct an online randomized experiment. In addition to reinforcing the causal inference from our secondary data analysis, causal mediation analysis of the experimental data shows that personal agent profiles influence satisfaction and the likelihood of customers expressing gratitude through the perceived warmth and perceived competence of the agents. Interestingly, while the effect on gratitude is mediated by humanization, we do not find a similar mediation effect on satisfaction. This suggests distinct pathways through which humanization shapes different aspects of the customer experience.