Twitter has accused Microsoft of using its data for unauthorized purposes. According to the New York Times, Twitter made the accusations in a letter to Microsoft CEO Satya Nadella yesterday.

“Microsoft may have been in violation of multiple provisions of the agreement for an extended period of time,” wrote Alex Spiro, the personal lawyer for Elon Musk in the letter, referring to an agreement Twitter had with Microsoft over usage of its data. In the letter, Spiro also accused Microsoft of using more Twitter data than it was allowed to and to have shared parts of this data with government agencies without permission.

After Microsoft refused to pay Twitter to continue to use its API last month, the social network is giving Microsoft a June deadline to share details about what it did with Twitter’s data for the past two years. The letter doesn’t mention if Twitter is already considering a lawsuit, however.

The missive comes just a month after Twitter CEO Elon Musk publicly threatened Microsoft with a lawsuit for illegally using Twitter data to train its AI models. Frank Shaw, Microsoft’s Chief Communications Officer acknowledged that the company received the letter from Twitter and was preparing its response. “We look forward to continuing our long-term partnership with the company,” the exec said.

In a quest to increase the company’s revenue, Twitter recently made big changes to its free API, alienating a lot of developers along the way. In addition to a “Basic” API priced at $100/month, Twitter’s Enterprise API now starts at $42,000/month based on usage and needs.