As several people have commented, it's common on phone conferencing systems, when entering the conference code "followed by the pound sign".
It's also used to check Verizon FiOS voice mail, where you enter it after entering your PIN.
As for the *, up until recently, I had a voice mail system where you used it if you were checking messages from a phone other than your own, to signal you'd be entering a phone (non-menu) number.
*...# is at least in Europe is used for many functions when you call it (e.g. topping up your prepaid phone, showing your balance)
Re:Octothorpe
by ealexhudson on Sunday January 25, 2015 @07:39AM
(#8942779)
You have to use # to get into a variety of phone conferencing systems, banks, and other stuff - it's the defacto "end of number" character at least here in the UK (e.g., "Enter your conference pin number, followed by the hash").
Haven't seen/heard of a use of * outside local PBX in years though.
As for "hashtag minor", it's a reshare of a second-person story, so I trust it about as far as I can throw it.