i say hello and you say hello (and then i say hello again)

oh, the social conundrums we face. take telephone greetings for instance:

'hello?'
'hello. may i please speak to penny?'
'this is...i am...that is, her...i am she.'
'great, penny, this is so-and-so from somewhere.'

and while i am still trying to figure out the grammatical puzzle of my first response, i am hit with yet another issue. how do i respond to the caller's self introduction? possible responses:
'oh…' - natural but insufficient
'ok…' - see above and a little rude
'hello…' - redundant, that’s how i started the conversation
'what do you want?' - sincere, but rude, i've been told
‘mmm-hmmm?’ - non-committal, one of my favorites, but doesn't exactly ooze intelligence
'oh, hello, how are you?' - the combo approach, completely insincere 99.9% of the time

social etiquette dictates the redundancy option but i just feel like there has to be a better way.