Don't bother with chat. You'll get better results if you contact cox.help@cox.com and include your full name, service address and a link to this discussion.
I had a similar issue years ago. Cox replaced the eMTA modem and reprovisioned it, but there was still no phone service. After 5 days, a tech checked my signal and detected an issue with the tap. (The tap is the Cox equipment at the pole that connects the Cox main line to the drop line to your house). The faulty tap was preventing phone service but wasn't affecting TV or Internet. A Cox tech replaced the tap and phone service was restored.
If a faulty tap is the cause of your issue, changes in weather conditions could cause the intermittent phone service you described. Contact Cox and schedule a tech with a long ladder to come and check your signal at the tap. If there's an issue with any Cox equipment at the demarc (Cox equipment box on the side of your house) or on their side of it, you won't be charged for the tech visit. You might consider subscribing to Cox Complete Care for $10/month. It will pay for the tech visit if there's no issue with Cox equipment. You can cancel CCC after 90 days. If you cancel before then, you'll be charged for any fees you would have been charged if you never had CCC.