Mormons being forced to go door-to-door

Mormons aren't forced to go door-to-door, it's absolutely a choice. In fact, Mormon missionaries pay their own way (less so in poorer countries, but still).

Perhaps you're thinking of Jehova's Witnesses? I don't know much about their proselytizing, but I have invited them in before and they don't seem particularly interested in following up, especially if you don't buy their stuff.