being that you are only supposed to have a max speed of 6mbps: the router should not matter.
but if you are getting week signal on your pc or smart phone, that could be the reason for your slower speed.
go to google.com type *whats my ip address*: on the top of the page it will say *your public ip address is...* copy and paste the number in to your address bar.
That will pull up your router configuration page. look around on the home page to find what your internet speed is, to confirm what your ISP told you.
Do you know what kind of router you have?