How do you use your time at work? At the end of the day, do you feel that you could have achieved more? It is very easy to become distracted or overwhelmed by unimportant or secondary issues during the working day, preventing us from being fully efficient.
Managing time effectively doesn't come naturally to all of us - but it is a skill we can all benefit from learning. Planning and prioritising are the two main components of time management:

Planning:
Working to a weekly plan or schedule can provide direction and reduce time wasting. Make time for your priorities, as well as your leisure and social time.

Prioritising:
Each day, make yourself a list of priorities to get through, and number them according to importance. Work through your list daily, and make a new one for each day. When making a new list, remember to transfer any tasks not done the previous day.
If the phone tends to disrupt your day, or interferes with your train of thought, you can deal with it in various ways:

1) If you have an answer phone or voicemail, use them. By answering every call you will cut into your work time. Screen them instead, and call back the less urgent ones when you are free.
2) Allocate times during your day to make and return calls, i.e. between 3 and 4 in the afternoon.
3) Keep your conversations short; don't stay on the line longer than you have to.
4) Move to a quiet or empty room if you have work that requires your full attention, away from the disruption of the phone.