Intermittent Service

I've been having constant issues with my business ADSL line over the past 2-3 months. My line speed has dropped from 6MB to 2MB over the last month and syncs at a different speed each time my router is rebooted.<br> Since yesterday my line has been dropping and doesn't sync for more than 5mins at a time. I was told by the previous technician \Your ISP has dropped your ADSL speed"I don't even see how this is possible as I use multiple ISP adsl accounts"