As usual, no harm asking the airline, talk to at least a supervisor, and explain the situation. Even they can't change the ticket, or give an iron clad promise, they might mention what they expect to happen or offer to make an entry in the pnr.

Then he should talk to TA, or his boss preferably, and politely explain that if he is denied boarding his only option would be to buy a ticket at the last minute price and claim all the loss from them. Would they not prefer the expenses to change the ticket, certainly lower now? Hand them a letter and keep copies. The idea is to be businesslike, not argumentative or confrontational.

If no resolution, dispute with your cc company and buy another ticket from a better agent.