Under the new “T-Mobile One” plan unveiled on Thursday, customers can get unlimited voice, texting, and data starting at $70 a month for one line, $120 for two lines, $140 for three lines and $20 for additional lines. Unlimited plans had previously started at $95.

New customers who wanted to pay less would have to opt for a prepaid plan, which start at $30 per month, T-Mobile said. Existing customers will be grandfathered and can remain on their current plans.

“A lot of people dab promotionally into these kind of offers,” T-Mobile CEO John Legere said on a call with analysts and reporters. “For T-Mobile, this is it.”

The new plans are subject to several limits, including all streaming video must be viewed at DVD-quality—not in higher resolutions—and customers that use more than 26 GB per line in a month could see their data rates cut to slow speeds.

The new plans will be available starting September 6, T-Mobile said. That is one day before the widely rumored start of pre-orders for the newest iPhones.

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Rival carrier Sprint (S) quickly announced its own new, cheaper unlimited plans after T-Mobile’s announcement. The Sprint plans started at only $60 but reduced the quality of music and online games as well as video.

T-Mobile (TMUS) Legere kicked off the Uncarrier strategy three years ago by eliminating two-year contracts. Subsequent moves, including cutting international roaming fees and exempting popular streaming music services from counting in data usage, have helped make T-Mobile the fastest growing mobile carrier in the country.

The move follows T-Mobile’s two larger rivals, AT&T (T) and Verizon (VZ), recently increasing prices for some plans, although adding bigger data allowances.

AT&T’s revamped plans did cut prices dramatically for larger data users.