The default prompt in Mac OS X is derived from
System Preferences ->
Computer Name. If that is set correctly and you still see
kellys-iphone in new terminal prompts, your terminal environment variable
PS1 has been set in either
.bash_profile or some other local file.
You can check which files set PS1 like so:
grep PS1 ~/.*
Side note: If you see a line like this:
[ -z "$PS1" ] && return
which just means "if this is not an interactive shell, disregard the rest of this file" - so that's not the droids you're looking for.
That should reveal a file that has a line akin to this:
export PS1="\u@\h\w$ "
Or, if I'm right:
export PS1="kellys-iphone-2:\w "
Edit that file/line to reflect what you really want. More info about custom prompts in OS X