Microsoft Corp. said its social media planning and scheduling tools for advertisers will no longer support Twitter, after the Elon Musk-owned social network started charging for access to its programming interface.

Musk responded to the announcement by accusing Microsoft of using Twitter data “illegally” and threatening a lawsuit. The billionaire, who bought Twitter last year, is changing the company’s policy to charge businesses for access to its stream of data.

Microsoft’s Smart Campaigns service assists advertisers in managing social media campaigns across platforms such as Facebook, Instagram, and LinkedIn.

Users of the product will be unable to create tweets and drafts, as well as view past tweets and activity, starting of April 25, the firm announced on Wednesday.

The software company is the largest investor in OpenAI, the AI research lab Musk co-founded before quitting in 2018. Musk is already launching his own competing AI initiative, Bloomberg reported.

Microsoft didn’t immediately respond to a request for comment.