Not sure where you are at but around the Houston area ever since Comcast took over from Time Warner all of their services went down the tube and we are seeing people dropping Comcast like crazy.

I'm no tech either, but did work for the phone co for 30 years.

Do all 3 services come to your house on one line? If so, I'd think that maybe it was the interior wire for the phone that comes out of the main junction box (from Comcast) likely on the outside of the house. If it is indeed the interior wire, I would think you would be responsible for maintaining it, or they would charge a hefty amount for replacing it for you. I would look the wire over well, on the outside and where it enters the house.

Does it maybe go through a crawl space where it might be drawing moisture? Is your phone ever noisy, but still working?

Is there maybe a way to disconnect the interior wire at the main box, and read it with a VOM to see if there is a short on it?

Sue

do your wires go underground ?

They could be damaged / corroded / deteriorated

worse when wet

I had similar problem with my tv channels getting snowy in the rain. I wrapped plastic around two outside connectors and the problem cleared. Then I got the cable guy to come out and replace the connections. It's either your line or the mainline.
Find neighbors with cable phone service and ask if they have this problem.