A La Paz agency in Sopocachi with a wide national list, including a trans-Andean run that starts in Cusco and crosses into Bolivia — the Peru–Bolivia combination that a lot of people actually travel and few agencies sell as one trip. They also sell the Refugio Los Volcanes and southern Amboró, which is a genuinely good three days that almost nobody offers.
Office hours are Monday to Friday, 9 to 12 and 2 to 6. They split their WhatsApp lines into sales, operations and emergencies, which is sensible; the sales number as printed on their website is mistyped, so use the operations one.