Same thing happened to me.. They kept blaming my Cisco ATA device. I started to have problems when there "outage" happened in March.
Even when I had phone calls forward to my cell phone I keep having problems. Needless to say it' wasn't my equipment at fault then.
Just like Centurylink, fast to point fingers and slow to fix for there own equipment.
That's what happens when they hire people that use to respond to "ding fries are done".