All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
The ugliness of such an action is self-evident and does not require a Fatwa; it involves cheating and deceiving the concerned authorities into believing that the caller's condition is a medical emergency, which is not true. It was narrated on the authority of Ibn Mas‘ood that the Prophet said: “Whoever cheats us is not one of us, and cunning and deceit are in Hellfire.” [Ibn Hibbaan]
Moreover, this action involves incurring harm on other patients who actually need ambulance services.
Allah Knows best.