Taxis are readily available at the Varenna-Esino train station for short hauls to the nearby villages and your hotel.
However, if you are looking for pick up from an airport or to arrange a day to some other destination (I once had a client do a day trip to Venice!! Expensive, but enjoyable.) You must book in advance, there is an email link to the service here and below are some more realistic destinations.
Autonoleggio – Taxi Service • Rent a car on Lake Como
Marco Barili • Via Pino 63 • Varenna (Lc) • Italy
Phone (+39)0341815061 • Mobile 3483548898 – 3485500787
website: Varennataxi.com e-mail: taxi.varenna@tiscali.it,