T-Mobile's iPhone Ad Angers BlackBerry Chief

Millions of once-faithful

BlackBerryBBRY

users have made a switch to an iPhone device over the past few years.

T-Mobile's TMUS

recent advertisement is targeting the remaining faithful users, and its irking BlackBerry CEO John Chen. T-Mobile is offering

Apple'sAAPL

iPhone 5S for $0 down. To promote the sale, the company ran an

ad poster that said, “Get the tools to do more. $0 down on iPhone 5S. GREAT OFFER for BlackBerry customers.” “As we were never told of their plans in advance, I can only guess that T-Mobile thought its great offer for BlackBerry customers' would be well received,” Chen wrote in a

blog post

on the company's website. “T-Mobile could not have been more wrong.” To customers, Chen said: “I can assure you that we are outraged too.” Many BlackBerry faithfuls took to

Twitter

to express their frustration, which prompted T-Mobile's CEO John Legere to apologize.

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A T-Mobile spokesman told

Bloomberg

, “We are happy to be a BlackBerry partner and apologize for any confusion.” T-Mobile also told Bloomberg that it will start providing free, expedited shipping of BlackBerry devices by the end of this week, “as an additional courtesy to our BlackBerry customers.”