DALLAS -- Dallas Mayor Mike Rawlings isn't holding back after hearing about hundreds of 911 calls being placed on hold.

"This is unacceptable. This is a matter of life and death for our citizens, and we've go to make sure we fix this,” said Rawlings.

He says the 911 system is in a crisis and city leaders blame T-Mobile.

“And if we can't do the basics in this city about answering phones, shame on them and shame on us,” said Rawlings.

Hundreds of callers are being placed on hold. When T-Mobile customers call 911, their phones automatically dial multiple times. All those calls register as hang-up calls, so 911 operators have to call all of them back, not knowing if the calls are real or not. It's tying up operators and forcing legitimate callers to wait.

Earlier on Monday night, at one point 360 callers needing police or fire assistance and couldn't get through.

Among those on hold was State Rep. Helen Giddings. "It took me 26 minutes to get an answer," Giddings said. Her friend needed medical assistance, frantic not knowing what to do.

As WFAA first reported a month ago, there are times when the 911 system is being overloaded by T-Mobile customers. What happens is when a T-Mobile customer calls 911, their phone repeatedly re-dials 911 and the caller doesn't even know it.

Hundreds of 911 calls in Dallas on hold, including state representative

Operators think those are hang-up calls and have to call them back, so callers using other carriers can't get through to an operator and are placed on hold.

The Dallas Police Department said it is frustrated with T-Mobile and its engineers who can't identify the problem or fix it.

"It's a grave concern because we have seen possibile solutions, and then once again those solutions do not hold,” said Deputy Chief Jesse Reyes.

The Dallas city manager and Mayor Rawlings say they are demanding answers and solutions.

“I want to solve this problem. If T-Mobile can't do it, we are going to get someone else that does it,” said Rawlings.

T-Mobile has repeatedly denied our requests for an interview or an explanation.