Should this tour operator be paying VAT?

Tourism Update received a letter from a US-based tour operator, with no physical presence in South Africa, asking whether his company may be exempt from paying SA VAT: 


We arrange visits to South Africa for groups of US students and teachers. Each year for the past several years we have sent two or three groups of roughly 20 people each to South Africa to learn academically and experientially.  


We contract with local South African hotels and safari lodges to accommodate our clients, and we work with coach companies and tour services companies to transport our clients locally and throughout the country.  Consistent with South African law, the local vendors have invoiced us for their base services plus VAT.  For 19 years we have paid the VAT on all services.  


And yet we have recently begun to wonder:  Have we been paying VAT when in fact we are exempt?  


Are you an internationally based tour operator with experience in this regard? We would like to hear how you have handled SA VAT and possible exemption. Please add your comment below or email us at editor@tourismupdate.co.za.