I have done it many times for economy (H) to PE over the phone in the U.S.. Previously, I would call in to book an economy ticket and wait for the receipt to be issued (it usually takes 2 to 3 days). Then I call them back to change it to PE and pay the USD$50 penalty + the fare difference. However, I told the agent about my company policies and my intention during my most recent booking (last week) in "H" face ticket. The agent was kind enough to issue me an economy booking receipt and cancel it immediately, then change my ticket to PE without charge me the penalty.^ So it is doable.