Thailand’s telecoms regulator has given True and AIS an additional six months to move all customers on their 1.8GHz networks, which are concessions from state-owned CAT Telecom, to other spectrum bands.

The 2G concessions with True Mobile and AIS’ subsidiary Digital Phone Company (DPC) expired almost two years ago, but the National Broadcasting and Telecommunications Commission (NBTC) has pushed back the cut-off deadline twice before. The previous cut-off date was 17 July. It is now marked (unspecifically) as January 2016, by which time 4G licences are expected to be issued.

True Move has about 700,000 customers on the 1.8GHz band, down from seven million last year and 17 million in October 2013, while DPC has only about 1,000 customers on its 1.8GHz network, the Bangkok Post reported.

The operators will need to return any prepaid mobile credits, which are estimated at THB20 million ($591,000), before the deadline.

The country’s 4G auctions have been delayed by more than a year since the military coup in 2014 and are planned for November and December. Two slots of 12.5MHz in the 1.8GHz band are scheduled to be sold off in November. That spectrum was previously held by True and AIS.

The NBTC is considering accepting an offer from dtac to return 5MHz of used 1.8GHz spectrum, which would increase the amount available to 30MHz.

In addition to the 1.8GHz auction, two blocks of 10MHz of 900MHz airwaves will also be sold off in December.

The auctions are expected to generate an estimated THB65.31 billion ($2 billion) based on a reserve price of THB16.57 billion ($507 million) per block for the 1.8GHz and THB16.085 billion per slot for the 900MHz block.

NBTC is said to be drafting regulations for the migration of AIS customers on its 900MHz network, which is a concession from state-owned TOT that expires in September.