Alarm system call phone when triggered

Hi, are you talking about calling, so a phonecall, over the mobile network?
If you are using the mobile app and have a mobile data plan, you could already receive notifications at a state change of these sensors.

If you haven’t seen it yet, take a look at:

I have been tinkering with an ESP device that can be used as a modem for the mobile network and which would work independently from HA haven’t got to working yet due to lack of knowledge. (have to pick that up again)