Russian telecom company MegaFon PJSC has sued Hewlett Packard Enterprise Co. claiming that the Silicon Valley tech company oversold its ability to complete a nationwide upgrade of MegaFon’s cellular network.

The lawsuit, filed Tuesday by MegaFon’s lawyers at Winston & Strawn in the Northern District of California, claims that MegaFon’s system has experienced a series of “cascading catastrophic failures” that have resulted in the “near shutdown” of service to its 80 million customers because of HPE’s “faulty system.”