MUMBAI, India (AP) — Vodafone says it has filed a court petition to stop India’s government from auctioning off rights to the cellphone spectrum it now uses for 18.7 million customers.

India’s second-biggest mobile phone operator says the planned auction is illegal because its license for the 900 MHz spectrum allows it to renew for 10 more years. Instead, the Department of Telecommunications decided to put the spectrum up for auction to allow new companies to bid on it.

Vodafone said Wednesday that it has petitioned the Delhi High Court challenging the auction. It said the spectrum now serves Vodafone subscribers in New Delhi, Mumbai and Kolkata.

The Department of Telecommunications had no immediate comment.

Vodafone also has an unresolved dispute with India’s government over a contested $4.4 billion tax bill.