Note that on many land-lines this will fail, as the calling party simply does not hang up, waits for silence on the line, then plays dial-tone down it. When you pick up again, it seems like you are connected to the exchange, but when they hear DMTF they just play ringing tones back at you, then pretend to answer as your bank and continue the scam. Bonus points to the scammers if they actually call the number you dialed and MITM the call for extra realism, only jumping in when you get transferred... ;) In fact, I bet you could program Asterisk to do this for you, or similar VOIP PBX software?