Not quite mobile telephony, but this was the most suitable catagory I could find.

Anyone know where I can download a user manual for the above DECT phone?

Or can someone tell me how to use the internal calls feature on it, and any other features you may know how to use (aside from making a normal phone call obviously )

Handsets are numbered in the LCD HS1 to HS4. To call internally, first take the phone "off the hook" (big green button), then hold down the directory button (looks like a book, picture of a phone underneath) for a couple of seconds, then press the single digit 1 to 4 corresponding to the handset number you want to call.

hi

I have just set up a new Audioline DECT phone to the phone line and would like to use my VS1003 as a 2nd phone.
I am not sure if this is at all possible.

It's normally possible with GAP compatible DECT phones.

Check the Audioline's manual for how to register additional handsets.