[kube-system]

Here's one for cable companies:

https://www.fcc.gov/media/customer-service-standards

And these banking regulations are too long for me to skim in too much detail, but they mention "telephone" 138 times in the context of various requirements of availability for certain functions and during certain times. One such example:

> 7. Telephone line availability. To satisfy the readily-available standard, the financial institution must provide enough telephone lines so that consumers get a reasonably prompt response. The institution need only provide telephone service during normal business hours. Within its primary service area, an institution must provide a local or toll-free telephone number. It need not provide a toll-free number or accept collect long-distance calls from outside the area where it normally conducts business.

https://www.fdic.gov/regulations/laws/rules/6500-580.html

But more specifically about government requirements, there's stuff like the ADA which requires specific means of access, and there's other things like the USPS USO which, for instance, requires 6 day per week postal service. I'm sure there are others.