Intex Mobile — power on/off button was not working

i buy intex aqua style mini on dated 19.03.2015. but with in one week power off/on button created problem. then i submitted the phone in intex care center on 31.03.2015.after this i take follow up everyday from intex customer care but no any respose from there side.. they just pass the time. every day they told that the part was not available. and some time they told that phon creates problem so it will check from inner side.. i just fed up from the customer care center.. the phone was creates problem in a week from the date of purchase, so i want new phone in the replacement of this. or other wise do the need full action.