Q. See question above 2) Should I have called Hatzalah and let the know it was B'H a false alarm and that they don't have to come anymore?
A. Madrich L'chevra Hatzala rules that one should call with a Shinui or in an unusual fashion, such as pressing the buttons with his knuckles etc.. The reason given is that statistics have shown that racing through the streets in an 'Emergency Mode,' imposes significant high risk to the driver and occupants of the emergency vehicle (Vayaan Dovid 3: 21, Nishmas Shabbos 5: 271, Betzel Hachochmo 4: 54, Tzitz Eliezer 20: 18: 7).
Besides, the Hatzalah rescuers may be needed for other valid emergencies.
Horav Shlomo Miller’s Shlit’a opinion is similar.
Rabbi A, Bartfeld as advised by Horav Shlomo Miller and Horav Aharon Miller Shlit'a