Traditionally, Mobile Network Operators (MNOs) use a set of Key Performance Indicators (KPIs) to measure the quality offered to their customers. However, these KPIs do not reflect the quality perceived by the customers because they are high-level and network-based metrics. Instead, Quality of Experience (QoE) monitoring of the most common mobile applications can help MNOs to determine when and where customer experience is degraded. In this paper, a customized tool based on Big Data Streaming is proposed to solve the needs of customer experience monitoring in a real-life MNO and to overcome the challenges of processing a large amount of data collected in 3G and 4G mobile networks. Moreover, real-life case studies of value creation through Big Data Analytics for telecommunication industry are also defined. Results show that the streaming data processing enables new opportunities for the MNO to take actions focused on customer experience improvement in near real-time.