extremely disappointed

My HD decoder which I got less than a year is suddenly not working. It's switches on but no signal, the 3 lights keeps flashing and does not go to the stable green. I have tried all troubleshooting possible, I am a premium customer and although my account is overdue by 200,it's active, so that is not the issue. I took my decoder to Maponya mall dstv branch so they can check it as it'd still within warranty and all they told me is they won't do anything because is overdue. The problem I'm having is not account related , it's device related which I paid for fully, I don't understand why they are making my account an issue. I would have not gone there if my account was an issue, how can I fix my decoder