Virginia-based Teligent recently sent form letters about the impending cutoff to a number of owners and businesses in Orange County, San Diego and San Jose. Teligent spokeswoman Tita Thompson won't say what other markets across the US might also be affected, but that the company will continue to service customers in Los Angeles.

Teligent's decision to stop servicing some markets means many building owners and tenants will have to find a new provider for their telephone and Internet service. Lining up new providers before the June 25 cut-off date could be a difficult task, because many such providers are backlogged with work.

Compounding problems, Teligent isn't the only telecommunications company to recently curtail service or file for bankruptcy protection. NorthPoint Communications, which had signed up more than 100,000 customers, has gone out of business and WinStar Communications also recently filed for bankruptcy.