Hi Fernando,
For a matrix you need multiple Destinations & Origins but you have only one of each. Please try just the Route API for a single trip. See https://learn.microsoft.com/en-us/bingmaps/rest-services/routes/calculate-a-route
A sample for your call it would be:
http://dev.virtualearth.net/REST/V1/Routes?wp.0=37.779160067439079,-122.42004945874214&wp.1=32.715685218572617,-117.16172486543655&key={BingMapsKey}
Sincerely,
IoTGirl