Cancelled call

I have called several phone numbers today and had no problem. One single number (it worked fine yesterday), right after dialing, without even ringing, it beeps three times and dies. If I look under call history, it shows "Cancelled Call". I have tried several times today, always the same result.

The person I called has an Android phone and had no problem calling me. I asked whether my number got blocked; no.

I can text, it goes through (send and receive).

I just don't understand what's going on.