Have you been put down by other people in the past for things you have said or done? If you have this may be the reason you feel scared to communicate to others. The way we act and feel about ourselves is usually determined by our past experiences so if you have had negative responses from people in the the past to things you have said or done it may have resulted in you feeling this way.
I am no counciller but I think that it may help if you can get urself a little book (that is personal to you) and write down all the good points about urself. If you find this difficult why not ask a close friend or family member to help you. I am sure that you will be able to come up with at least 3 things whether it be that you are caring or even something as little as u have nice nails! You need to start thinking about ur positive qualities. Each day if you do something that you feel can be seen as positive, note it down in ur book. Set yourself a weekly or even daily challenges such as 'today I am going to answer at least one phone call in a confident voice'.
Next, write down a list of some people that you would like to be like. Think about why you would like to be like them, is it they have money, nice boyfriend, a loving family, confidence? Finally, think about what you can do to help you be more like the way you want and as long as it is achievable, make a list and do it!!!!
With regards to speaking on the phone, I used to be terrified as I got a job when I left college working in cold calling sales! OMG, I was only there a couple of months and by the time I left I was terrified of the phone for fear of rejection (past experiences again!). I eventually got over this because I had to. One thing that helped me deal with my 'phone phobia' was the thought that the person on the other end did not know me and if I did not know the answer to a question I just said "I'm not quite sure about that, if you just hold for one moment I