Those are not bait and switch unless the buyer is told that the introductory price was the permanent price. Bait and switch is a form of fraud where an offer is made and accepted, technically constituting a legal contract, but then the offerer reneges on the deal, claiming some sort of snafu beyond his control. Having not made the offer in writing and having apparently made some sort of honest mistake make the buyer unlikely to hold it against him, even though it is often technically a breach of contract. Oh, well, the buyer reasons, I may as well trade up and finish this thing, now that I've put so much time and energy into it. And that completes the bait and switch.

Simply offering "first three months free, then we start charging" is not bait and switch. It's a perfectly valid offer.