Vox poor service

Vox installed my system in middle January... Eversins I have had dropped lines and most of the time a low download speed. I'm paying for a 50/5 line but sit most of the time with like 15mbs or less. I've been sins day one on the phone with tech support with a tune here and a tune there and at the end still no satisfaction. I'm very disappointed with vox service. *** Martin