Are you looking for a specific name for the combination of these two types of widgets or just a general name for input fields that are linked together? Would your definition also incorporate the country code selector that you often see in front of the phone number input field?
I don't think you need a specific name for the combination of these two types of widgets, since it is a contact detail input form/pattern that can be implemented in a number of different ways. For example, instead of the dropdown you can use a radiobutton group to select the type of input.
I think the abstract pattern would be linked form input fields, much in the same way that a button group links separate radiobuttons or checkboxes together logically. If you want to be even more pedantic, you could say that linked form input fields can be of a heterogeneous nature (like a dropdown linked to a text input field) or homogeneous (like a button group containing radiobuttons).