Why I feel scared talking on phone when the guy says hello when I called for a job inquiry ?

Before making the call, do some deep breathing exercises and focus on your breath to calm your mind and your body.  Write down what you want to say and speak slowly.  You might want to practice what you will say before making the call.

Try to be casual.  It will relax you and make you sound more confident.  For example, you could say, "Yo, s'up with dat job Bro?"

cause youre afraid you wont get the job

Pre-plan what you are going to say by writing notes, and just read them off.

When calling about a job, you need to understand that YOU have what they want, but they don't know it yet.  so, you have to be ready with points prepared which will educate them on what you have.  Get a piece of paper and write down your important points.  Get someone to help if you need to.  Read these over and over and over again until they become ingrained and easy to say.  That way, when a prospective employer asks a question, you have a prepared and practiced answer.  You aren't trying to think of an answer you KNOW the answer.  Practicing these answers make it easy to say, and THAT will show confidence.  

cause u are not a social person, u are shy