Pecking away at your phone is a rookie mistake. Taking a personal call can occasionally slide, but there is no quick recovery when you are preoccupied with your mobile device. Relegate all communication to your computer. Most businesses run on Google Apps, which is perfect because it can look like you are responding to emails... but little do they know you are talking about how crazy Scandal was last night (Can you believe how thirsty Edison was?). Import all of your friends' personal emails into Google Talk, and make sure to click "Go Off The Record." No reason to have your chat logs archived in your inbox because that creates evidence against you. Microsoft Lync users can also have Google Talk contacts IM with them by scheduling an online meeting.
Other options for texting/messaging include Google Voice, Facebook Chat, and more. Some cell phone providers like Verizon even provide an online messaging system that can be utilized to communicate with the outside world while keeping a low profile. Now proceed to get those IMs and SMSes off.