Some Amazon cloud customers woke up Friday to a surprise bill estimate that said they owed billions of dollars for cloud services they had never used.

Amazon confirmed Friday that it is trying to resolve an error in its Amazon Web Services (AWS) billing portal that showed some customers were owed millions or billions in cloud computing costs.

In an update to its status page, Amazon said it began seeing inaccurate billing data late Thursday. But on Friday morning, the company admitted that “reverting a recent change did not resolve the issue.” Amazon said the change relates to its billing calculation subsystem.

The good news for customers who were told they “owe” millions or billions to Amazon is probably out of the woods. The billing estimates “do not reflect actual usage or charges,” Amazon said.

According to several screenshots posted by Amazon customers on Reddit, one customer was quoted an estimated billing of nearly $2.5 billion for AWS usage this month, while others received similar alerts, ranging from a few million dollars to hundreds of millions of dollars.

An Amazon spokesperson did not immediately respond to a request for comment. The issue is expected to last several more hours, according to Amazon’s status page.