The Bing Maps for Enterprise imagery REST API is documented here: https://learn.microsoft.com/en-us/bingmaps/rest-services/imagery/get-a-static-map. Your call is not using this format.
If you are looking for an exact area, you may also want to review the direct tile option https://learn.microsoft.com/en-us/bingmaps/rest-services/directly-accessing-the-bing-maps-tiles and ask for the exact tile at the exact zoom level you want. You only need to call the REST imagery API above once for the meta data then directly pull the tiles you need from the URL provided. Note that these tile server pointers are updated regularly so you should do a fresh meta data call for each session.