mobile sent for replacement since 3 months but not yet received

i had purchased iball mobile which stopped working within 3 months so submitted for repair under warrantee but the company said it cant be repaired due to unavailability of parts so it will be replaced but it is since last 3 to 4 months comany is refusing to return the mobile as the model is not available so please helm me to get my mobile back as i am facing a big loss due to it so please help me out of this.