Rang off after about 4 rings: robot?

No message. Calls twice daily, morning and night. Goes to answering machine but hangs up. Sometimes the call shows up as "private", sure it is the same origin as the timing is nearly always similar.

Has rung 2 days in a row and hung up when it went to answer machine. They dont leave a message

Caller: I don't know!

Every day we have received a call from this number and there was no one there. I called the number back and had a recorded message saying that it was the Heart Research Institute soliciting donations. I called the number for "Reception" on their website and, after many rings the phone was answered by a lady who apologised that the receptionist was not there and would call be back later

As soon as I said "hello" they hung up

Caller: Unknown

Same as others, it hung up before it went to voicemail

2nd time this number called in 2 or 3 days. Rang off before it went to answering machine, both times.