Cannot unlock my Samsung Galaxy A12

I'll be traveling abroad and need my Samsung Galaxy A12 unlocked to be compatible with foreign SIM card. At first I submitted an online request to unlock, but immediately got a message from AT&T saying I have to use their device unlock app. The app doesn't show anything and wouldn't let me unlock my device. Even if I called the support number the app recommended, an automated voice keeps saying they can't recognize my phone number... Did someone have the same issue and get it resolved?