How do scammers use fax machines against your iPhone?

2 AM I get a text message on my iPhone supposedly from a local credit union tell me to call a certain phone number. I was too curious. So I called on the land line. The answering device sounded like a fax machine. I hung up immediately, went to the credit unions Web site and saw text messaging fraud alert.

How are these crooks using a fax machine to attack a text capable phone?

I didn't say the fax machine sent the text msg. I said the fax machine was on the end of the line they want you to call. So if you called that number with your iPhone how would they attack your iPhone?