Here's a link to the chart, all credit goes to Powdinet: https://puu.sh/uRsNV/c1eab6f481.svg

Once you study the chart, understanding it becomes pretty easy. Powdinet explained some of it to me, and I've posted what he said in an additional chart which lists all of the calls that get terminated after a certain point. That chart is here: https://docs.google.com/spreadsheets/d/12g8aB04oT50FzOz8u1hJ4FQ-4QyDJU3hlHUiF3ZwQ9o/pubhtml?gid=708905257&single=true

I've also posted what he said, below.

*Powdinet explains parts of the chart: -ambient_phonecalls are basically what you'd call "absolutely useless" -they serve no purpose other than to add some more story for casual gameplay

-phone_player phonecalls are the most important, they block the player's progress until they are answered

-Chat_Phonecalls are those where you call a character and they talk about events related to completed missions -They aren't used in a speedrun at all -When a chat_phonecall is set, the previous one for that strand is simply replaced by the new one -since all chat_phonecalls are for roman, there will always be a maximum of one chat_phonecall at any time

-The ones that say "Wait" block strand progress until they come in, while the others don't -Texts without "Wait" are not needed at all to progress the game, and as such should be avoided (though it's highly unlikely there's a path that avoids a lot of them)

-The script seems to check for the text messages sequentially from 0 to 58 for an available text -I should correct and say that what I said is valid only if the text message timers are exactly the same -if one of them is earlier than the other, even if both expired, the earlier one will be chosen. By earlier I mean in terms of time, of course*