Does anyone have optimum online and voice and use Demension E310 with these?

I am trying to figure out how to use my fax capability with Optimum Online/Voice.

My computer came with a 56K modem but the Cablevision company gave me an external modem. I tried faxing using the fax wizard and it gives me an error message that it doesn't detect a dial tone.

I have had 7 calls into the Dell support center and no one can answer this question!