A registered Bolivian company — Quechua Connection 4WD SRL — on the corner of Bolívar and Cabrera, selling the standard one- and three-day salt flat circuits plus something most Uyuni agencies do not: self-driving tours, one and two days, where you take the wheel of the Landcruiser yourself.
They make a point of bilingual local guides with at least ten years each, which on the Lagunas route to the Chilean border is not a marketing line. That road crosses 4,900-metre passes, the vehicle is your shelter, and who is driving it matters more than the hotel.
They publish a landline and, separately and clearly, a WhatsApp mobile. The two are different numbers.