Microsoft faces a 1 billion pound ($1.27 billion) dispute in the U.K. over how it charges customers who buy cloud software services that rival its own Azure, the latest antitrust challenge to the U.S. tech giant’s approach to licensing.

The lawsuit brought on behalf of multiple parties by litigation specialist firm Scott+Scott alleges that Microsoft is leveraging its dominance in must-have computer operating systems and unfairly charging business customers more if they purchase its Windows Server and use it with the tech giants’ main rivals’ cloud platforms.