As promised, here's a timeline summary.

2/21/25:
AMEX:Pending refund on AMEX for ridiculous amount. I assumed would be corrected.

2/22/25:
AMEX:Entire large amount posted to AMEX in the evening, with -5x MR points pending.

2/23/25:
AMEX:Dispute started, credit wiill remain on account until investigation is complete, check back in 48 hours.
AA:Phone agent escalated to her supervisor/help desk, who suggested I misunderstood the currency conversion and said everything looks correct on their end, but will send a message to the refund department to investigate. In the meantime, send a summary email to Revenue Protection at [email protected]. (NOTE: never received reply.)
AA:In attempt to escalate, sent emails to Robert Isom and Carolyne Truelove.

2/24/25:
AA:Email from [email protected] saying the refund amount is correct per their records and I am misunderstanding the currency conversion. Replied with screenshot of AMEX transaction.

2/25/25:
AA:Twitter: Sent DM with summary and AMEX screenshot. Received reply that their records show refund is correct. Sent reply that that is not possible.
AA:Received phone call from agent referencing my email saying the refund dept has so far determined the amount is correct. I expressed that this cannot be possibly correct. Later, received a follow up call from AANGEL at corporate (customer relations/customer success) saying they may have found the problem, and are working with the refund department to address this. Said will follow up with me with progress and gave a direct number.

2/26/25:
AMEX:After 48 hours, called to get update on dispute. Per rep, dispute team needs more supporting evidence from me. Cannot transfer to them. They will call me according to rep. No time frame.
AA Twitter: Received reply confirming it is correct in their system and to contact AMEX.

2/27/25:
AA: AANGEL called to report refunds Leadership is now involved and is in contact with the AMEX Director of Payment Processing. Will also follow up with Leadership at Revenue Protection to make sure no overlapping investigations are occurring.

2/28/25:
AMEX:4 transactions posted: 3 totaling ~$30M, and another refund for nearly $300K.
AA:Told AANGEL about the transactions and requested a contact at AMEX because the regular customer service there is not helping. She said she will make a call and then call me back. Called back to say AMEX will reach out to me. AA investigation has determined that it is an AMEX error.
AMEX:Received call from AMEXANGEL: Apologized, they have been in communication with AA. Provided direct number to reach her. Primary investigation is through vendor/merchant services. Putting in the fix by end of day Monday 3/3. Will reach out to fraud/abuse team to make sure no adverse action taken. Will also merge the dispute to close it out.

3/1/25:
AMEX:Corrections posted for the original error, but not the ~$30M. Account blocked for "high credit exposure" per chat rep; call fraud dept. No answer at direct number (not working weekends). Left message. Called regular number and transferred multiple times between customer service, disputes, fraud, credit, customer experience, RLA (Responsible Lending Act), CPS (consumer product services), ultimately reaching Segment A department. Seg A informative and helpful, but cannot do anything over the weekend per supervisor given the high reported balance. Never seen a balance this high. Will put in a new report.

3/2/25:
No activity.

3/3/25:
AMEX:Called AMEXANGEL. Explained my card was blocked over the weekend. She sees that original error has been fixed but the $30M error has not. Asked her to just have the 4 incorrect transactions dated Feb 27 deleted, not adjusted. Will follow up.

Disputes Team called me. Was very confused. Informed him to follow up with AMEXANGEL.

AMEXANGEL followed up to say she has escalated with multiple teams and still pending resolution, is told they should be in after midnight tonight. AMEX is unable to "delete" any transactions, so must post corrections instead.

AA:Discussed still not resolved, so sent a message to Leadership to follow up with AMEX. AA believes the currency conversion error came from AMEX side with this particular currency and it may have affected other people as well, so they have temporarily stopped transactions in this currency.

3/4/25:
AMEX:The ~$30M has been credited back, but still have an "extra" ~$300K credit, plus currency conversion charges of ~$75K. Will send message to have this fixed too.

3/5/25:
AMEX:AMEXANGEL reports fix should be in 24-48 hours. Will also contact Credit team to try to unblock card now that balance is lower. Card unblocked in the afternoon.
AA:AANGEL followed up with me to see if transacftions fixed.

3/6/25:
AMEX:AMEXANGEL called and adjustment was issued today, so should post tomorrow.
AA:AANGEL followed up with me to see if transactions fixed.

3/7/25:
AMEX: AMEXANGEL confirmed all corrections posted. Later offered compensation.
AA: AANGEL sent email saying please call back if any issues.

I departed on trip, so unable to follow up with AA.

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3/24/25:
AA:Followed up with AANGEL to confirm AA investigations consolidated and closed. Offered compensation.