Good question! My mobile only gives me a choice of its own annoying ditties. I'd use The Kerry Polka- nice and lively to summon you to the phone, simple enough so that you can get a full 8 bars (i.e. the first half of the tune) in 36 notes, and the one note that is below the 'octave +1' range sounds ok transposed up an octave. It might just put you off the tune for life though...

Noreen

I'm pretty sure it's on JB's tunefinder site- I'll look it up later if you're interested.