I enroll AutoPay and At&t cut my program without any notification

Sorry to say, your account has apparently been closed and your balance lost. There are a few reasons that could have happened. When was the last time you made a payment to your account and how much was the payment? Your account balance had an expiration date. If you went past that expiration date, the balance was lost. If your balance was $0 for more than 60 days, the account was closed. That is how prepaid has always worked.

Another possibility is if the phone associated with your account was no longer compatible with ATT’s network due to the 3G network shut down and needed to be replaced. Customers with incompatible phones were notified by text during 2021 but since you were not in the US, you probably did not receive the notice. ATT started closing accounts earlier this year that did not replace their phone.

Either way, there is no fix to your issue.

All this ⬆️

I'm guessing the program you're probably on is the one where you're allowed to switch to one of the pay per use plans while you're outside the United States so that your balance isn't reduced by usage. Those plans also no longer exist. The $2 plan the $0.25 plan were terminated in January. Anyone on those plans who did not have active usage on AT&T network found their accounts canceled.

Unfortunately there's nothing you can do. There isn't even any record that you had an account with AT&T

The answer is unfortunate and shows unfairness.
 This is a unilateral action. 
that at&t knows when i'm online 
it doesn't make sense to send a text message
 when i'm not available,
 that's why the company has my email.
 The company did not bother to warn me
 and thus caused me damage More than that, 
stealing money for nothing, it's impudence and unfairness
 that's not how you run a business. be ashamed

Never the less, it's how all prepaid works, and it's the agreed plan requirements.  If payments on a prepaid plan are not made on a regular basis, the account is closed. 

The pay per use plans must be refilled, just like any other plan must be refilled, or the services canceled. If you deposited $100 in 2020, it expired in 365 days.

After 365 days, you had to refill, or the service is canceled and the account closed and all funds forfeit. If you haven't been to the United States and haven't refilled in over 2.5 years, your service was terminated long ago.

Even if AT&T did email you, it would have been over a year ago.

You agreed when you signed up, even if you didn't read what you signed. 

https://www.att.com/legal/terms.consumerServiceAgreement.html

Section 3 covers prepaid. 

If your account was closed because you were using a phone that needed to be replaced, we agree that wasn’t fair and ATT should not have done that...but they did that to many customers. Don’t blame us, we are other customers.

Hi Yeiv1952, we're sad to hear that your AT&T PREPAID plan was closed and would like to give you more details. 

As the ACE @sandblaster mentioned, if the phone associated with your account was no longer compatible with ATT’s network due to the 3G network shut down and needed to be replaced. Customers with incompatible phones were notified by text during 2021. AT&T started closing accounts earlier this year that did not replace their phone.

Let us know if this helps, and thank you for contacting the AT&T Community Forums.

Jeff, AT&T Community Specialist