As mobile carriers rush to turn on 5G networks, two important aspects that remain mysteries are just how much the new plans will cost and whether unlimited data will remain.

In a new interview with PC Mag from the MWC tradeshow, T-Mobile chief technology officer Neville Ray provided the first insights from a major U.S. carrier saying that the self-proclaimed "un-carrier" will not be more expensive than the company's existing 4G LTE service and that the plans will remain unlimited.

T-Mobile plans to launch its 5G network sometime during the first half of the year, though exact locations or timing for its first markets remain unknown.

Earlier this week, it was revealed that the company's wider 5G network will be launching in the second half of the year. This will use lower bands of wireless spectrum than the high-frequency millimeter wave (or mmWave) technology the company will deploy its first 5G network on.

Samsung's Galaxy S10 5G, which T-Mobile has said on its website it will carry this summer, is designed to work with mmWave technology but lacks the proper chips to tap into the wider 5G network T-Mobile will be launching later this year.

Chips that support that lower band network are not expected to arrive in phones until later in 2019.

T-Mobile confirmed Ray's statement to USA TODAY.

John Legere, T-Mobile's CEO, previously pledged that the company would not raise rates for three years if its pending $26-billion merger with Sprint were approved by lawmakers.

Last year, the company said that it would first launch its 5G network in New York, Los Angeles, Dallas and Las Vegas, making those cities the possible first four sites for T-Mobile's mmWave spectrum.

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The company has mmWave spectrum in eight to 10 cities across the country, though it is not exactly clear which ones or when it will turn on 5G in those markets.

AT&T so far is the only carrier to turn on its mobile 5G network, though it has yet to launch a phone or detail how much a smartphone plan will cost with 5G. (It too, will have the Galaxy S10 5G later this year.)

The only device on AT&T's network is a $499 mobile hotspot, which it charges $70 per month for 15GB of 5G hotspot data. While the network launched late last year, those in one of the 12 5G cities still need to fill out a contact form before they'll be able to get their hands on the device.

Sprint said this week that it will launch its 5G network in four cities in May before rolling out to five more before the end of June. The company did not, however, detail pricing for its 5G plans or its first 5G phone, the LG V50 ThinQ 5G.

Verizon will be the first to have the Galaxy S10 5G during the first half of the year, but it has yet to announce when and where its first 5G cities will launch or how much its service will cost.

Follow Eli Blumenthal on Twitter @eliblumenthal