Slow Internet after storm

The three computers at my house were previously fast when connecting to the net. After a pretty bad storm, they are now at a snail's pace, and disconnect often. We have tried resetting the cable modem, with no luck. Can I go out and buy a new modem myself and just hook it up? Or do I need to call the ISP (Knology) and wait for them to come out and put one in?

Sounds like there is some moisture somewhere in the external line.
I would get the ISP/Line Company into to have a good look at it, and test the line for noise.