Not responding to calls

"Good morning has anyone got a contact number for bolt in Maitland ,my sister used bolt services yesterday from Houtbay to town and when she got out the car she left her phone behind. She immediately called the driver and he answered then the call cut. She then tried calling him again and he went into voicemail. We have been calling non-stop and he is still on voicemail and her phone was ringing but now also on voicemail. We have tried calling the head office in CT but no reply Kind regards