Problems with broadband speed are usually more likely to be related to phone line problems than with anything you can fix yourself.
If you computer is connected to your router with a cable, and you're getting low speeds when you run a test here
http://speedtest.btwholesale.com/ , then it's definitely a problem with your phone line.
(That test site assumes that you're getting your broadband service through a phone line. If you're using a cabled service use this test site instead
http://speedtest.btwholesale.com/ . Remember to ensure that nothing else is using your broadband connection, such as a Now TV box or other internet-based television service).
If your computer is connected to your router wirelessly, try it with a wired connection instead. (If the speed you get improves considerably you'll know that it's a problem with your wi-fi and you can ask again here. If it remains low you'll know that it's a problem with your phone line).