Dell AIO 964 Printer

I've been working with someone on setting up their Dell AIO 964 machine, and everything works fine except for one small thing.

First off, here's how the telephone system is set up:

LANDLINE --> DELL 964 --> ANSWERING MACHINE/TELEPHONE (it's another AIO thing)

Now, whenever you call the landline, the fax machine on the Dell is supposed to answer after 3 rings. If no fax is detected, then the Dell is supposed to let the answering machine pick up. Atleast that's what the manual says.

Sadly, it does not work this way. Instead, when you call the house, after the third ring, the caller gets the annoying fax sound and is never forwarded to the answering machine.

I found a way around this so that the answering machine will pick up first; I just set the answering machine to pick up at 4 rings, and the fax machine to pick up at 5 rings.

But then what happens if someone sends a fax....

So my question is, why won't the Dell AIO forward the call to the answering if there is no fax detected? Everything is connected correctly. The manual doesn't mention having to change anything in the software to enable this. I did look on Dell's website and there is a firmware upgrade, but I want to know if there is anything else I can try in case that doesn't work.

If you need anymore info or if I didn't explain this clear enough, please let me know. Thanks!