worst service provider

sir
i hv been using idea postpaid from five years almost but now i want to change it to prepaid.But company is not cooperating at all instead they are disturbing me as i hv ragistered my request to idea office for three times and they cancelled it by saying that i hv not picked up their call.they call at such an awkward hours and for vry short ring they give that i ws nt able to pick this.I complaint this to idea help line but useless… plz hlp