So many things wrong with this:

1. That's a fax machine handshake not a data modem.
2. That's a LOT of data to be hissing over dial-up in a highly compressed GSM voice channel. That kind of interface would be pushing it even on 10 Mbps broadband.
3. The background noise would have had that handshake repeating over and over

Credit to @riskable@programming.dev for their comment in another thread that inspired the post title.

Obviously they use a different data protocol. You've never heard of it, It goes to a different school.

I would really love to meet this data protocol that can modulate 100 Mbit traffic to fit inside a 13.2 kbps voice codec. I totally will not be patenting it and getting rich from it.

Bleep, bleep, bloop

The background noise would have had that handshake repeating over and over

Clearly she is actively noise cancelling the pickup microphone.

That's a fax machine handshake not a data modem.

She must be hacking a government fax machine to read out the buffer and fetch the information from the ducuments in there.

That's a LOT of data to be hissing over dial-up in a highly compressed GSM voice channel.

She quickly improved her phone and cracked the gsm authentication to make the phone establish multiple connections in parallel.

Devils advocate response (I'm not really this invested in T3)

1. If I remember correctly you could set an analog modem to reply first with the fax handshake before initiating a data session so that you could use one phone line to accept both incoming faxes as well as incoming data connections. Listening to the audio it actually sounds like two handshake files happening at the same time because the first doesn't finish before the next one begins, which would be wrong.

2. Perhaps there isn't actually much data moving. As in perhaps its receiving names in text responses, and the terminator is searching its own local databases of images to match the text it received from the connection.

3. I'm not sure what you mean by this one. The handshake happens at the beginning of the session after dialing and pickup. As soon as the session negotiation is done the sound would just be a low whirring sound. Most modems mute the speaker when it hits that phase, but there's no technical reason it has to. You could configure your system to continuous play the sound even after handshake, but there was no reason to do so.

Really though I know its just Hollywood doing Hollywood stuff.