Well the PIR has alarm contacts so you could use them maybe with a relay just to trigger the input on any autodialer , there many cheaper devices which will do the just b for you on eBay
For example
https://www.ebay.co.uk/itm/Alarm-Installer-Auto-Dialler-with-Controllable-Relay-/233783581818?mkcid=16&mkevt=1&_trksid=p2349624.m46890.l49286&mkrid=710-127635-2958-0
They have different versions , but I would recommend a cheap monthly contract SIM , you will kill your credit quick otherwise