Thanks for calling (our company). The office is currently closed. Office hours are 9am to 6pm, Eastern Time. Please leave a message at the tone and we'll call you back on the next business day. Thank you.
Whether you’re out for the day or are off for the week, the first rule of an out of office voicemail greeting is: let callers know when you’ll be back! You’ll save them the frustration of continuing to call and yourself the hassle of listening to redundant voicemails. It’s also a good idea to set the expectation of whether you are answering messages while you’re away, and who they can reach for assistance in your absence.

Our voicemail service on our cloud VoIP system is like a digital answering machine which not only allows you to hear your VM messages but also allows you to divert them to emails. Our powerful business voicemail features work on all our VoIP phones…
In practice, most businesses are simply handling this on a case-by-case basis since COVID is a temporary problem. Most home networks can handle the extra load as long as the employee makes sure that other latency-sensitive traffic, like gaming or video streaming, is kept to a minimum during the hours when they need to talk. If some home routers develop problems, IT staff simply build a queue and handle those one at a time. Sometimes they'll be able to access the router remotely with the employee's permission, sometimes they'll have to walk that employee through configuration steps to fix the problem. Sometimes the employee will just have to live with it unless the company springs for a new router or a higher bandwidth tier from the employee's ISP.