False Sales

In February 2015 I was contacted by sales and offered to move to SmartHome Advance which has 20GB of data per month with 4mbps line, instead of my 10GB/month I initially had. Since then the technical system still shows I am allocated 10GB/month instead of 20GB. After using 10GB in the last month my speed was throttled down to 0.3mbps. Forthe past months I have tried to rectify this with no joy. I keep getting passed from pillar to post with no competent person to rectify the issue. The technical department keeps blaming the sales dept. And sales dept. says they see 20GB/month allocated, while the technical dept. says they only see it as 10GB/month allocated. Could I please have a senior person who knows what to do resolve this issue ASAP.