Hi there
My phone is passcode enabled! :-)
I have learned that to phone an emergency contact, the home button needs to be pressed so that the screen to enter the passcode appears. Then on the bottom left, there is an active word Emergency - when that is pressed, again at the bottom right, there is an active part called "Medical ID *" (in red). Once this is pressed, the person at the top of the list of the people entered as emergency contacts in the Health app is dialed. This, for me is the only logical explanation. That it happened is incredible, but my bill for the calls is real!
To phone my daughter otherwise means either bypassing the passcode screen, Which is seemingly impossible, or somehow my passcode is entered on the passcode screen, then the phone app is selected, and then my daughter's number is dialed, which is "+***********", where the *'s are all numbers and + signifies the international dialing code preceding a country code. To do this correctly 5 times in sequence is beyond the realm of possibilities.
If there is an easier explanation, then please share as I want to prevent it happening again! :-)