My parents (in the US) purchased a non-refundable ticket for a 4-month trip from a travel agent. I'm pretty sure it's a oneworld reservation (includes AA, BA, IB, etc). The price, connections, and flight times were excellent. One of the destinations is Saudi Arabia, and it is the only destination for which they need a visa. They applied for the Saudi visa with the understanding that they'll get two-month validity and one month stay. Their current itinerary places them in SA on July 16 flying in from London. However, on June 10, the Saudi embassy stamped the passports with only one-month validity (probably due to a change in policy that took effect after the passports were submitted). Obviously, this necessitated that they change their London-Jeddah flight with BA from July 16 to July 10 or earlier. Likewise, the exit flight from SA will also need to be changed to make sure they don't overstay.

We received the passports three days before the trip and started scrambling to make the changes. The TA offered an alternative itinerary with totally different flights (much worse of course) and asked for $800 per person (claiming it was all for the airline). AA, on the other hand, had us on the phone for a couple of hours, and came out with nothing for London-Jeddah (they looked from Jul 1 - 10). Finally, they offered us a connection flight for which they asked $3000/person which of course we declined.

We tried to work with the TA to find a more reasonable alternative, but he said he can't find anything better than the $800/person. We asked why he couldn't just change the affected segments, and he said that he cannot change the itinerary within 7 days of travel except by changing all the flights. He said our best chance was to travel to London and talk to BA about finding a reasonable alternative. He also said that if they start their trip, he will not be able to help them in any way with the current itinerary.

This morning, my parents commenced their trip to London. We're distressed as we don't know how to solve this issue or what options are even available. We're also not very trusting of the TA at this point. Please share your general advice and (if you can) specifically touch on the following issues:

1) Is the TA correct in claiming that he cannot change the current reservation after the commencement of the trip?

2) What about his claimed inability to change the reservation within 7 days of the flight except by changing all the segments?

3) What is the best way to approach the airline in London? Office or airport counter?

4) Who should they go to: BA, AA, both?

5) What other options do they have at this point?

6) If they cannot find a reasonable trip to SA, and decide to return home (US), will they lose the rest of the segments or is there a way to postpone the remaining part of the trip?

Sorry, I know I'm asking for an essay here, but our situation is quite desperate and we need guidance/clarification. Thank you.