Vox slow fibre speed

Queried slow internet speeds on 10mbps frogfoot line. Getting max of 4mbps when running a speed test. Vox uncapped voice also poor quality. Contacted there IT department multiple times. Was told they cannot help me if I do not have one of there modems as they need to run a broadband test which was not working. I'm paying for 10mbps fibre and they cannot even be bothered to send out someone to test the line. Very poor service.