Your agent is Orbitz/Expedia. Calling Air France won't help.

The agent is not obliged to follow the rules that any other agents may follow [such as the rules that AF apply, or agreed to waive, had you been their direct customer]

I really doubt that Air France has any such rule about 5 hours - this sounds more like internal Orbitz/Expedia policy. Appealing to Air France over the head of your agent isn't going to help now. Orbitz are the ones you went to, dealt with and paid money to. They are the only ones that can now consent to giving you a refund.

Refunds in such cases are usually offered on a discretionary basis, all the more so when through no fault of the traveller the flight is no longer suitable.

If Orbitz are still maintaining that there is a 5 hour rule, ask them to demonstrate where this is publicly stated on their website.

I would ring back and hope for a more customer-oriented agent.

However, a 4-hour change in the context of an intercontinental flight (I assume, at least, this is an intercontinental flight you are talking about) advised well in advance may not always be judged sufficient grounds for cancellation. Are you connecting to another flight? How has the overall journey time been impacted? Have you investigated having Orbitz rebook you on different flights/different routings closer to the original flight times?