Nokia 5130
Unwanted call

My name is Satya Sindhu Bhattacharya. I live in Baruipur, Kolkata-700144. I have a nokia expresso music 5130.

For the last 2 weeks an unknown number is harassing me even at late night. Please tell me how will i block this number from calling me? Is there any call barring service pin code that will do this thing? please help me.