Called back after a missed call and got "The number you have dialled is disconnected. Please check the number is correct before dialling again." or something close to that, which repeated a few times, then it said, "N. N. G...1." and hung up. The voice was kind of distorted and shaky, kind of like an old cassette that's a little warped if you know what that sounds like. Kind of bubbles and crackles at times.

Anyway, probably a robocall.