Dialing was way more fun than hanging up. (and less reliable) - Brian Johns

But it was always fun to trick newbies into typing '+++', waiting for 'OK' and then typing 'ATH'. - Kevin Fox

ATZ. OK. AT S7=45 S0=0 V1 X4. OK - Mo Kargas

On many modems, it would work without waiting for OK (although the original Hayes command set required a delay after +++ before popping the modem back into command mode, many modem manufacturers did not implement that). And so, tricking a user into sending the characters "+++ATH<enter>" would disconnect them. - Tudor Bosman

This was often done automatically: CTCP PING messages in IRC channels, or the "-p" argument to the Unix ping command. - Tudor Bosman

(Both work along the same lines: send a message to the user's computer and request that it be sent back unchanged, ostensibly to measure delay, packet loss, etc. In this case, sending it back would make the user's computer send the +++ATH<enter> sequence, and get them disconnected.) - Tudor Bosman