Things They Should Invent: require advertisers to make good on any offers they spam you with

From time to time I receive a flyer in my mailbox from my telecommunications provider, promoting a service I already use at a lower price than I'm currently getting. The fine print says this offer is only available to new customers.

I think this should be illegal. I think, because they arranged to have the offer put directly in my personal mailbox, the offer should be available to me personally. Any company that contacts you directly (by mail, phone, email, direct message, or any other medium) with an offer should be required to give you that offer.

This wouldn't necessarily have to apply to mass media advertising, like on TV or in newspapers. But if each individual has their own copy of the ad that has been sent directly to them personally and landed in physical or virtual space that is under their personal control or their household's control - so that you can say "This is my copy of this ad" - the advertiser should be required to make good on the offer.