As an alternative to Skype, you could use "vLine link": https://vline.com.
The advantage over Skype with this use case is that you don't need to add them as a contact (especially if it turns out to be someone you decide you don't want to stay in contact with).
The advantage over Skype with this use case is that you don't need to add them as a contact (especially if it turns out to be someone you decide you don't want to stay in contact with).
Disclaimer: I work for vLine.