On Thursday, October 8, 2015 at 8:50:09 AM UTC-4, Steve Stone wrote:
If you believe that all your home telephone gear and wiring is in good
shape consider opening a trouble ticket with your telco.

I've had similar problems in the past with my DSL line and it turned out
to be a bad line card at the central office.

Good luck,
Steve

From what we've heard so far, that would be the logical step.
And if they need to come out, be there, with a test phone in hand.