1). Connect to http://www.speedtest.net/ That's your speed to Verizon. That's the definitive way to determine where the problem lies. (You just have to know what the numbers mean, and how to interpret them, but it's the first thing any professional checks when the problem is "slow speed".)
That's what you buy, and that's all you and Verizon can control. If that's lower than what you're paying for (at least 768kbps if you're not paying for more), call tech support. (And good luck - tech support - or, rather, the joke that Verizon calls tech support - is one reason I don't use Verizon.)
2) Your download speed is the slowest of - your connection to Verizon, their connection to the internet, the path you get on the internet to the provider of the server you're downloading from, that provider's connection to the internet, the server's connection to their provider and the server's upload capability. The slowest part of that is normally the internet itself - normal speeds for any but local connections is about 600-700kbps, regardless of how fast your connection to your provider is. (But with a 6mbps connection, you can do 10 600kbps downloads at the same time.)
Which one is holding down your particular speed? Tracert (or traceroute if you're not using Windows) to the server you're downloading from. The slow node is the culprit. What do you do about it? Choose a closer server. There's no other answer. The problem - if it's not your connection to Verizon (and speedtest.net is the way to determine that - is out on the internet somewhere, and no one is going to fix that. (One of the problems is that 60% of the bandwidth of the internet is wasted by spam emails. Eliminate them and download speeds would go up. But we can't eliminate them.)
If you want a "click here" solution, you're not going to get it. The problem is either a) between you and Verizon, and they have to fix that or b) on the internet and you have to choose closer servers.