The second operator in Tupiza with a real website, on Avenida Pedro Arraya rather than in the central block where Tupiza Tours and La Torre sit. The site is published in Spanish and English with a Boliviano/dollar switcher, which suggests they sell to walk-ins and to people booking from abroad in roughly equal measure.
They are reachable by a contact form, a mobile and a WhatsApp Business link. Which number that link goes to they do not say.