Use the C/Call label (aka 'call context') for conversations that make more sense to have on the phone.

In particular, complex discussions that can be solved more quickly on the phone, and any emails that could lead to confrontation (e.g. a misunderstanding, or critical feedback). The problem with stating anything negative in an email is that, because it is just black & white text and lacks 80% of the communication spectrum (voice, face, etc.), it will almost certainly be read with much more aggression than you ever intended. It is therefore certain to aggravate the situation. Remember, call don't email if you ever have to criticise!

When you are near a phone you can pull up all the C/Call conversations, make each one, remove the label and if necessary, add the results of the discussion to the conversation (so it is all stored in one place).