Nina Simone Lawsuit -- If You Steal Her Song -- You're A Sinner, Man

Don't mess with the High Priestess of Soul.

Nina Simone's 1965 hit "Sinnerman" is an R&B classic ... but that doesn't mean a phone company can boldly rip it off ... so her heirs are suing for $1 Mil minimum ... TMZ has learned.

The lawsuit -- filed by Simone's estate -- accuses smartphone company HTC of using her song in its TV commercial without obtaining the rights.

We reached out and touched someone at HTC ... so far, no call back.