CORONADO, Calif. (CBS8) -- Rebecca Zahau's cell phone logs show she engaged in a series of phone conversations and traded several text messages in the hours before her hanging death at the Spreckels mansion in Coronado.

News 8 obtained two pages of AT&T billing logs from the 32-year-old's cell phone, which family members said was a newer-model phone using the Windows Phone mobile operating system.

The cell phone records confirm Zahau listened to her voicemail for two minutes at 12:50 a.m. on July 13, about two hours before her estimated time of death.

Adam Shacknai, the brother of Zahau's boyfriend, called 911 later that morning at 6:48 a.m. to report Zahau was hanging nude from a second-story balcony at the mansion. She was gagged with her hands and feet bound.

Officials said the voicemail was the trigger that led Zahau to hang herself off the courtyard balcony of the historic mansion, owned by her boyfriend, pharmaceuticals tycoon Jonah Shacknai, 54.

Two days earlier, Jonah Shacknai's 6-year-old son, Max, had suffered grave injuries from a fall off the stairs while under Zahau's care.

"We know from the investigation that (voicemail) message that was left on her phone was to inform Rebecca of Maxie's grave condition and imminent death," said San Diego County Sheriff's Sgt. Dave Nemeth at a news conference earlier this month.

Zahau's sister, Mary Zahau-Loehner, said detectives told her that Jonah Shacknai left the voicemail on Rebecca's phone around 12:30 a.m. on the morning of her death.

Detectives said the message was erased and officials will not confirm who left the voicemail. That does not sit well with the Zahau family attorney Anne Bremner.

"The message, whatever it was, is forever erased," Bremner said. "They're pinning this entire suicide conclusion on a phone message that no one has ever heard."

Zahau's cell phone records did not log any incoming voice message from Jonah Shacknai on the evening of July 12.

AT&T spokesperson Georgia Taylor explained why some incoming calls may not be included in the billing log.

"When someone calls you and you do not pick it up, or the call was not received, it goes straight to voicemail," Taylor said. "It is not logged on your bill per se. If you're not answering it or if your phone's turned off, it's not going to register."

The cell phone log showed that Rebecca had three phone conversations with her sister Mary that night, the last one at 9:25 p.m.; and multiple text messages were passed between the two sisters from 9:44 to 9:53 p.m.

According to the logs, Zahau also received a text message at 10:41 p.m. from Nina Romano, 41, the twin sister of Jonah Shacknai's second ex-wife, Dina Shacknai. Dina is the mother of Max Shacknai.

Contacted by News 8, Romano said she sent the text message to ask if she could come by the mansion.

Family members said Rebecca had picked up Romano at a San Diego airport on Monday afternoon, several hours after Max Shacknai's fall down the stairs.

"I just wanted to talk to her about the accident," Romano said. "And so I sent her a text message that said, ‘Hey are you around? I'd like to come by,' and I never heard from her. She never responded to me."

Romano recalled sending the text earlier in the evening, though, and questioned the 10:41 p.m. time stamp on the AT&T call log.

While she was in town, Romano said she stayed at her sister Dina's house, which is also in Coronado.  Romano said she left San Diego on Saturday, July 16, the same day her sister's son, Max, was taken off life support.

Also listed on Zahau's cell phone logs was an incoming call at 7:09 p.m. on July 12 from Coronado Bay Urgent Care in Imperial Beach.

Rebecca's 13-year-old sister had received stitches in her leg at the urgent care center on Monday, July 11 after cutting herself on glass. The center was calling to confirm a follow-up appointment for Wednesday.

That appointment was canceled because Zahau had already dropped off the teenager at the airport in the afternoon of July 12 for her return flight to Missouri.

While at the airport on July 12, Zahau picked up her boyfriend's brother, Adam Shacknai, 48, who arrived on a flight from his hometown of Memphis around 4 p.m., said Mary Zahau-Loehner.

Since Rebecca's death, Zahau-Loehner has been trying to get her sister's phone inspected, but the sheriff's department will not release it.

"I would like to see a forensic download done on the phone," Zahau-Loehner said. "We're asking for our property back so we can start our own investigation."

The Zahau family believes Rebecca would not have killed herself in such a manner and has asked for the investigation to be re-opened.

"My goal is for Rebecca's voice to be heard and I will do anything to find out the truth of what happened to her," said Zahau-Loehner.