ADSL Performance

Since December my ADSL has been consistently slow. I've tested with different ISP's and the issue persists, I've logged faults but they are continuously closed without resolution. I've been told that it is a congestion issue. Then why close the call without resolving the issue? I'm being billed for a 4 mbps line but I'm not getting close to this speed. Someone should look into why the congestion issue is not being resolved, why faults are being closed without resolution, and why people are being billed in full for an inconsistent service.