CEO John Legere made the announcement via a live Periscope stream.
"I just want to tell you that this has been the biggest launch ever for us."
The company saw four times as many pre-orders for the iPhone 7 as compared with the iPhone 6.
"The first four days of the iPhone 7 launch are by far the biggest ever for T-Mobile. So I don't know what else everybody else is doing. But how about this, it's like four times bigger than the iPhone 6 for us at the pre-order stage."
Notably, Legere also revealed that the most ordered color is "Black".
"Yes, it's... we call it basic black, matte black is the most pre-ordered item."
T-Mobile's announcement will be important to investors as Apple has decided not to reveal launch weekend order numbers for this year.
Here's the statement Apple released to CNBC.
APPLE STATEMENT TO CNBC:
"We expect iPhone 7 and iPhone 7 Plus will be incredibly popular with customers and we are thrilled to begin taking pre-orders on September 9. Customers will receive their new iPhones starting September 16.
In years past, we' ve announced how many new iPhones had been sold as of the first weekend following launch. But as we have expanded our distribution through carriers and resellers to hundreds of thousands of locations around the world, we are now at a point where we know before taking the first customer pre-order that we will sell out of iPhone 7.
These initial sales will be governed by supply, not demand, and we have decided that it is no longer a representative metric for our investors and customers. Therefore we won' t be releasing a first-weekend number any longer. We are reiterating the financial guidance for the September quarter that we provided on July 26."
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