Dallas officials are working with T-Mobile engineers to determine what is prompting a flood of "ghost" calls that have forced hundreds of 911 calls to be placed on hold and may have slowed the emergency response to two people who died.
Dallas resident David Taffet confronted mayor Mike Rawlings on Wednesday to say it took 20 minutes to get through to 911 after his husband stopped breathing last week.
At one point, Mr Taffet was disconnected. He was placed on hold when he called back. His husband died at hospital.
A six-month-old child died during the weekend after falling from a bed.
His babysitter tried calling 911 three times but kept being placed on hold.
Officials said phantom calls are coming from T-Mobile phones to 911, leading to long wait times.