The copper phone network is being retired nationwide. The FCC stopped requiring carriers to maintain it, and carriers responded by raising copper prices and letting repair times stretch to weeks.
Some businesses get a formal shutoff letter. Plenty just notice the line getting worse and the bill getting bigger until service quietly ends. Both paths end the same place.
Phones are the easy part. The lines people forget are fax machines, fire alarm panels, and elevator phones, which have code requirements about how they must be replaced. Those need specific hardware, not just a VoIP adapter from Amazon.
If your business still has any copper line, get the replacement scheduled on your calendar, not your carrier's. Moving early is cheaper and calmer than moving during a shutoff window.