CM600 very slow download speeds - No splitters!

Hello all. I have a CM600 modem that over the last few months has been experiencing download speeds in the 1-5% range of what I am paying for from Comcast. I have called Comcast numerous times (it's almost a twice weekly event now) and they have refreshed the signal several times, as well as sending a technician out to my house a couple times. Neither of the technicians could find anything wrong with my line, and after each time they came out, the speed would go back to normal for a couple days. I do not have any splitters or other accessories attached to the line, and I have power cycled the modem several times. Finally I called the other day to speak to an actual representative who checked my equipment, and she said that her system was showing an exclamation point next to the router. She told me that it showed that there was some kind of noise filter on the router. Is this a feature that Netgear has that I can turn off or is there anything else I can do? Thank you for reading, and for helping.