What happens if you text and call a disconnected number from an iPhone?

I'm trying to figure out if someone's number has been disconnected. When I call it says your call can't be completed as dialed no matter what phone I call from. When I text from my iPhone it appears that the text was sent and I don't get an error invalid message and the text doesn't turn red. Could this just mean that incoming calls are not working for this person?

The person may not have paid their bill, or may have gotten a new number, so until/unless they contact you, you will be without their phone number.