We’ve been getting a lot

We’ve been getting a lot of junk faxes at work lately. They usually offer us things we don’t want, and even if we did want them, we’d have to dial a premium rate number to get them.
Today we received two faxes offering to get us off the junk fax distribution lists. Sounds good so far. But how do we achieve this? Ah yes, by dialling a premium rate number.