NODE switch via DV Switch mobile


I know this must have been covered many times before but I am new to this.
I have successfully set up DV switch mobile and can converse via my Andriod phon and my Shari PI3U.
At 80 yrs you might understand how proud I am. (With more than a little help).
I cannot , via the DV switch, connect to other nodes.
I presume it is meant to be possible.
When I have connected there is a line Dial String.
If I enter the number of a node to connect to e.g. 41522 and press send the number is then in a block of green and nothing more happens.
is there something in asterix which is meant to make this work that I have got wrong/
Assiatance would be appreciated.