A1 / Telekom Information:

https://www.a1community.net/telefonie-und-netz-446/community-hinweis-wie-erkennt-man-betrueger-anrufe-249312

Websites for checking suspicious calls

https://www.wemgehoert.at/

https://at.shouldianswer.net/

Website of the Austrian phone regulatory agency

/ also for checking numbers

https://www.rtr.at/TKP/service/rufnummernsuche/RufnummernsucheWeb.de.html