Just smile. Don't growl when the phone disturbs you for the umpteenth time; answer with a smile, even if it kills you. When calling, check it's a convenient time. Don't use first names or discuss personal stuff if you've never met.
What to say? Plan your conversation before you dial; keep it short and sweet. Never say anything you wouldn't put in writing. Avoid phrases like 'I shouldn't be telling you this, but...' Interrupted? If colleagues distract you with a message, ignore them unless it's life or death (even if they're taking the coffee order). If needed, don't just slam down the phone: explain, apologise and call back within 15 minutes.
Voicemail. Update your message daily. If screening colleagues' calls, use the standard white lies. Don't say: 'He's nursing a hangover in the mens.'
Using a mobile. Don't embarrass yourself by shouting, and switch it off when it might disturb others, especially in meetings. Remember that a vibrating phone in your pocket will get noticed.
Conference calls. Treat them like ordinary meetings, so no pulling funny faces because they can't see you. Introduce everyone and use the handset, not the squawk box, to start and end the call.
TXTing? Don't use it for serious business, and certainly not to sack people, as the Accident Group did when it fired 2,400 workers with 'unfortunately, salary not paid'. Execs might get FYI, but TTYL?