Calls breaking through iPhone DND

I was gobsmacked. I had set DND on my watch, and as usual, it propagated to the phone. I went to sleep as normal. (I have to have second sleep for a whole lot of reasons). Then two calls in succession within 3 minutes of each other. I have DND set to accept NO calls, and I have the allow calls if there are two within a couple of minutes set to OFF. Those calls should not have got through. They were from Diabetes Australia, but when I checked the number against the Truecaller database, its registered as Telstra. Is there something that says let telstra calls through no matter what? (Yes they left a message, thats how I know who it was)

I always thought that function was on the phone side of things (like silent/vibrate settings). The only other setting in there talks about silencing calls while the phone is unlocked (or not). I’ve had strangeness where the auto function and the manual function seemed to interfere with each other if you crossed the auto threshold resulting in calls that I wasn’t expecting to make it through, although on checking it was actually turned off for no good reason.

I know I have had weirdness in the past with the phone NOT ringing at all (which was solved by resetting the carrier settings and making it redownload everything. Optus had stepped me through some code entered into the phone dialler like 23# and then hit call (NOTE THE REAL CODE) which had the phone acknowledge something the ask to download carrier settings. Not sure what this was but I can’t seem to find it in Google right now.
There is also a reset network setting under: General → Reset → Reset Network Settings (although I’ve never tried this one myself).

I’ve also had issues where the audio just stopped working completely (on two very different devices and different accounts within the space of 24 hours) which were resolved with a simple reboot.

Exactly. And it works beautifully. It just dint work for this particular call. My phone is not supposed to receive any calls. That is, the calls are supposed to be bypassed. They were not. They were silent (I had the sound switched off with teh side switch), but they vibrated the hell out of my bedside table. The reason I got message was not because the system worked but because I refused to answer the calls. I should not have known the phone was ringing. Thats the whole point of DND. I havent changed anything or rebooted, but because I forgot to switch DND off, I missed a call this afternoon.