Frontier Communications is facing a flurry of customer complaints after acquiring millions of phone, television and Internet accounts in three states from Verizon

The $10.5 billion transaction to acquire Verizon’s landline businesses in Florida, California and Texas roughly doubled Frontier’s Internet and television subscriber base, and will boost its annual revenue to nearly $10 billion from $5.6 billion in 2014. It is part of Frontier’s plan to build a profitable land-based telecom business as other companies invest in wireless technology and media.

The rise in customer complaints also shows the difficulty of handing off millions of customers to a new owner. Verizon has sold other landline assets to companies like FairPoint Communications and private-equity firm Carlyle Group LP, which bought Verizon’s Hawaiian operations. Both telephone carriers later filed for bankruptcy protection. But this isn’t new territory for Frontier, which has struck such deals before.