free call; toll-free call
Refers to a telephone or voice/video call that incurs no charge, typically via internet services like Skype, LINE, or WhatsApp, or a toll-free number.
Using Skype, you can make free calls even overseas.
This app supports free calling.
通話料 is the call charge itself, while 無料通話 is the free call service or act.
無料 is a general adjective meaning 'free of charge', whereas 無料通話 specifically refers to a free call.
Compound of 無料 (free of charge) and 通話 (telephone call).