Purpose The purpose of this study is to explore the characteristics and potential effects of teaching and learning through audio teleconferencing (dial-in) with a cell phone. In addition, the study aims to identify the associations between the audio teleconferencing and video teleconferencing in a 12-week postgraduate course. Design/methodology/approach The study is a cross-sectional survey conducted at the Department of Educational Innovations at the Kwame Nkrumah University of Science and Technology from March to June 2020. The purposive sampling technique was used to sample 100 postgraduate students who registered for a course in the department. The data for the study were collected using the System Usability Scale (SUS) and 17-item self-administered eQuestionnaire. Multiple Linear Regression analysis, ANOVA, Independent sample T-test and Mann–Whitney U-test were used to estimate the differences in course achievements of students who experienced education through audio teleconferencing and those who experienced education through video teleconferencing. Findings In total, 59% of the participating postgraduate students chose to attend the synchronous online lectures via audio teleconferencing (dial-in). The participants gave a high SUS score (SUS > 80.3; Grade A; Excellent) for audio conferencing service. Among the students in the audio teleconferencing cohort, the results evidenced a strong positive linear correlation, (r (57) = 0.79, p < 0.05), between the individual adjective ratings and the SUS scores. There was marginal significance among demography of students in the audio teleconference (AT) cohort with regards to their perception about the dial-in lecture. There was no statistically significant difference, (t (98) = 1.88, p = 0.063), in the achievement test for AT students and video teleconference (VT) students. The instructors and the students were satisfied with the AT. Practical implications Based on the students’ preference, AT offers equal benefit as VT with regards to system satisfaction and perceived quality of online teaching. AT, as teaching modality, should be an option for students who reside in communities with high latency internet connectivity. It is recommended that instructors are trained on how to engage and motivate students via AT. Originality/value Higher education institutions in Ghana are facing decisions about how to continue learning and teaching through flexible pedagogy, while keeping their faculty members and students protected from the COVID-19 pandemic. Many of these institutions have canceled the brick-and-mortar education and other conventional learning practices and have instructed faculty to adopt online teaching through synchronous video teleconferencing platforms. However, the learning experience is not the same for students who reside in remote or rural communities with low bandwidth. There is very little research in this topic, especially in developing countries like Ghana, and the present study aims to bridge the gap in the literature by exploring the characteristics and potential effects of teaching and learning through audio teleconferencing (dial-in) with a cell phone, in the context of a 12-week postgraduate course.