The bots are spamming chat in the cities to keep their ads visible to passersby. While it won’t entirely eliminate them from advertising, you could decrease their ability to SPAM by implementing some sort of restriction. The average person doesn’t talk at the same interval that they are sending text.
Perhaps you could limit how many times a person could repeat the same thing in a period of time. I’m sure they would start a loop of different texts, though. Or perhaps how many times someone could say something within a short period of time, which is a good feature to have for trolls anyway.
There are a number of chat/text restrictions you could use that wouldn’t flag a human user, and they would cut back on a lot of work in the future because as bots get reported, new ones will just get created.
I’m sure someone else has a better idea, but I’m standing here in a busy city unable to read my chat screen or even scroll through it because of 2 bots spamming, 2 were recently removed and then a new one showed up.

