So having an interpreted phone call can feel odd....to say the least!
The interpreter has the thrilling choice to either wait and figure out the full sentence, leaving an awkward silence that seems to span the eternity of time. Or run with what they've got filling in the gaps as they go with whatever 'filler' AKA noise, erm, 'soooo' and other stretched out oddity they can crowbar in and look like a total moron who can't string a sentence together.
On the other end of the line sits a bewildered individual that is totally confused by the whole situation and just wants to get off of the phone.
All the 'fillers' and freindliness in the world wont make that phone call feel 100% 'normal' but at least now you know why! Why not throw etiquette to the wind and roll with it....you might even like it!