In this research, we investigated whether the use of GeoGebra Augmented Reality (AR) can foster students in conceptualising a mathematical object by manipulating its different semiotic representations. We designed and implemented, with thirty university mathematics students, a teaching sequence on paraboloids using GeoGebra AR supported by GeoGebra 3D with the aim of fostering students' work with different semiotic representations. All the activities carried out during the teaching case study were video-recorded, transcribed, and analysed according to Duval's Theory. Results show how GeoGebra AR facilitated students in the manipulation of different semiotic representations of paraboloids involved by highlighting the cognitive activities of treatments and conversions which emerge while conceptualising the mathematical object at stake.