By using small focus group discussions, the present study aims to gain insight into students' perceptions about the impact of WhatsApp use in their learning process. More specifically, this study presents a cross-cultural analysis of British and Spanish university students' personal beliefs about the effectiveness of using WhatsApp to complete group tasks outside the classroom. In so doing, this research represents a step forward in technology-enhanced instruction insofar as it not only incorporates the voices of learners themselves, but also contrasts students' beliefs with their group interactions on WhatsApp. The exploration of these WhatsApp interactions makes it possible to argue that the use of WhatsApp does not seem to create a natural context for non-native language users to produce contextualise relevant utterances while interacting with native English speakers. Furthermore, the results show that the lack of pragmatic competence on the part of the participants prevents them from communicating effectively. These pragmatic failures, in turn, have a negative impact on their interpersonal relationships and make them develop negative opinions towards the use of WhatsApp as a learning tool.