Why not ? It's a simple charitable request, no real different from those that have occurred for years. Aside from the request is for a continuous regular contribution, which seems to be the favoured option of charities these days. You could put a sign in your door telling cold callers where to go.
Or if you want hassle go text a donation to a favoured charity and find they call you back and badger you to make this regular contribution or that regular contribution, and are quite insistent you can find something you agree to. Don't like that, well what about ....