What hotline did you visit? Sounds more like a cold line, lol.

That's damage from the Four Lined Plant Bug, pretty common on mints and basil, in particular. So, you have an infestation rather than an infection.

You might consider informing your hotline people....these insects are common enough in some locations that they should be able to offer the correct information.

Thanks. I know the hotline is staffed by volunteers, but I was still a bit confused by their answer.