They do it anyway
and we didn't have this problem before the breakup of AT&T. Slamming is against the law in my state, and the phone companies do it anyway. Just read the fine print in any sweepstakes form or contest form that you fill out, usually by agreeing to their rules, you agree to switch your LD service. The same goes true for some of the free stuff on the web, like free gifts, downloadable software, etc. If they ask for your address and phone number, they might slam you to their service. I think someone filled out some of these forms and used my name and phone number. I am suspecting a few people from my former employer as they used to pull in-office pranks like that. One joker used the ipinger service to have it call up my work number at different times of the day, he also used Photoshop to modify employee photos and printed them out as a joke, he would lower our chairs to the lowest setting, he would get in very early in the morning and mess with the stuff on our desks and rearrange the items, etc. He is a real good friend with the boss, and he even got a promotion to Project Manager, which he quit after a few months of doing that and reassinging his projects to me and another developer, then he went back to being a programmer analyst. They kept him, and let me go?
"Will code Visual BASIC for cash."