Was it installed recently, were you present when it was installed. How did you get the homehub 4
Are you sure you have had Infiity installed. You say that the owner pays for Infinity. Have you confirmed with the owner that Infinity is installed and if it is have you asked the owner where the modem is.
Could it be that you were sent a HH4 by mistake and you should have had a HH5 sent.