All English speaking hotlines have a pool system so it doesn't matter which number you talk to. You would be having the same pool of agents.

If still the agents aren't able to book you an emergency exit seat, don't worry too much. QR passengers do not tend to pay for emergency exit or bulkhead seats so they are generally empty unless the flight is fully booked. If you check-in online at the time it opens, you would be able to purchase them online right on the spot unless they are taken.