Provided you get an agent who understands the rules.
During my last DONE3, I went to make some simple time changes (free changes) and the person as the AA rates desk that the lounge agent spoke to wanted to charge the reroute fee.

Carriers may charge a service fee, which is different to the reroute fee. Such a fee should be the same as any other ticketing fee they might normally charge. In 11 years of RTWs, I've only been charged a service fee when making a change once. When I made a reroute before departure (-xORD-ATL-ORD- to -xDFW-RDU-ORD-). That was the service fee, reroute fee and tax changes.