No service after taking the full payment by D-Voice/I-on

I have paid to D voice/ I-on for Internet service. The Internet is not working for 4-5 days and no service is provided even after registering the complaint. I went to the office also, they said the will fix it ASAP. But, after reaching home no one came to fix the issue. I got frustrated as I have paid for 3 months in advance.