Paraguay's bookable supply is unusual, and it is worth knowing the shape of it before you start emailing.
More than half of what a traveller can actually book here belongs to an institution rather than a company: SENATUR runs the Jesuit missions and the Asunción walking tour, ITAIPU runs the dam, a Mennonite co-operative runs the Chaco museums, a diocese runs two of the best museums in the south, and conservation NGOs run the reserves. Those bodies answer landlines and email, in office hours.
The private operators are a different story. Every one of them found in this sweep answers WhatsApp, from a 1986 receptive agency in the capital to a four-room lodge in a mission village.
So: for anything state-run, write or telephone, and expect a slower answer. For anything privately run, message it.