Constant Internet Drops From Modem?

In the past week I have been getting totally random disconnects from my modem. Sometimes it works great, other times it will essentially cease to function as it tries to sync to bells lines, it seems to be worse at night from what I've seen. I have called my ISP over 4 times, had 3 separate techs come to my house and replace everything from the router to the Internet port down the road.The only thing that has not been replaced is the actual phone jack in my wall but every tech has looked at it and said its functioning fine. I am at a loss, and on the verge of canceling my service with my ISP at this point. Problem is I cannot get rogers for various reasons, so bell is my only option for high speed internet, so canceling with them sorts leaves me high and dry.