On December 15th, I landed in Korea and did not have my phone service, so I used 600MB of data under the International Day Pass. The next day, I had my local SIM working and disabled my AT&T sim from my phone (eSIM only, so I cannot eject). I also turned off International Day Pass on my account, thinking I wouldn't need more roaming usage (I did not know I would be billed only for the day I use it). I submitted the request to remove my IDP on December 16th, but the removal of IDP is backdated to December 15th, and AT&T charged me $1200 for the data I used under International Day Pass. I tried asking AT&T support, but they said the charge was "valid" and could not do anything for me. After days of back and forth and a two-hour support session, they finally admitted it was an AT&T error. They said,
It was an AT&T error; expect the charges to be waived. A credit of $1150 would show on the account within 24-48 hours.
For AT&T customers, never take away your International Data Pass. It was interesting for me who grew up in Korea, to see that in the United States you should protect and exercise your own rights proactively. If a similar thing happened in Korea, I could've simply filed a dispute to the local government on my phone and they will basically autopilot everything to the conclusion. Whereas in the United States, it is my job to negotiate and discuss the terms proactively, for my best interest.