“the worst interuption in shul are the 5,6,7 mishulachim that collect during shma or shmonei esreh”
We don’t permit it; only before Barchu and after chazaras hashatz/leining.
What’s worse than a cell phone going off? Answering it in shul. We don’t permit cell phones to be ON in shul, yet there is always someone whose phone rings and even someone who will answer it.
However, people who learn or davin while the Rav is speaking in shul are worse than those who use their phones in shul.