Relations between BlackBerry and T-Mobile have turned frosty after a promotion last week saw T-Mobile BlackBerry users offered a cheap iPhone.
The email promotion offered some T-Mobile customers an iPhone 5s for US$500, a saving of $150 on the retail price.
BlackBerry has seen its user base contract in recent years as consumers were won over by iPhones and Android devices, so many current BlackBerry users are either those on company-issued devices or the very loyal. And the T-Mobile promotion didn't sit well with the BlackBerry loyalists.
After a flurry of Twitter messages and blog posts, T-Mobile CEO John Legere responded Sunday by telling his Twitter followers: "BlackBerry users, I'm hearing you loud and clear. Let me work with the team and get back with you."
He followed by pledging that T-Mobile doesn't have any plans to abandon BlackBerry devices: "We give our customers choices, but you don't have to give up your loyalty. We will continue to support."
But the damage had been done.
On Tuesday, BlackBerry CEO John Chen took to the company's blog and said BlackBerry was "outraged" by the "clearly inappropriate and ill-conceived marketing promotion."
"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. T-Mobile could not have been more wrong," said Chen.
He went on to say the relationship between the companies was "once productive and profitable for both BlackBerry and T-Mobile" and that he hopes the companies can "find a way forward that allows us to serve our shared customers once again."
BlackBerry declined to comment further on the status of its relationship with T-Mobile.
Martyn Williams covers mobile telecoms, Silicon Valley and general technology breaking news for The IDG News Service. Follow Martyn on Twitter at @martyn_williams. Martyn's e-mail address is email@example.com