Change default caller app (changing Facetime settings doesn't work)

Hi there,

I want to start SIP calls out of my chrome browser (ERP Cloud Software) and when I choose "use default caller software" to call, it always opens Skype. I already found here in the community a hint how to change it: In FaceTime you can choose in the "settings" a default caller app, which should do the trick. BUT: I switched it to the one I'd like to use ("Telephone"), but still: always Skype pops up. I cleared browser cache and everything, but still... Any ideas??

thanks for help :)