There are two options to show the phone nr or other fields.
You can add a reference selector and set the property readonly to true. This is the best option if you want to show one or two fields of the reference.
Or you can place another readonly dataview inside the dataview you are showing. There you can show as many attributes from the caller as you want. You can even show associations from the caller.
If you want to show only a few (1 or 2) fields from your associated object a readonly reference selector is the best option. When you want to show several attributes of your reference a readonly dataview will be faster.
One additional remark is that you have to set the "Create object" parameter on the readonly dataview to false. If you don't a new object for the referred item will be created every time you create a new referring item.