Wrongly invoiced and struggle to get back the refund

This is probably the worst express courier ever. they owe my partner a refund for a parcel invoiced wrongly on his name which were not even his (waybill no: ***). what a *****. They promised the he will be refunded on the 10th July already almost a month ago and nothing is happening. he's been corresponding back and forth with the following staff but for sometime now not being able to get hold of any of them with no feedback at all: Sheldon Dean Da Silva, Mathapelo Melato, Tertia Botha, Siyabonga Malinga