Despite the fact that it doesn’t offer the iPhone, T-Mobile in the U.S. has pledged to support its customers who are using the devices on their network, according to a new report. The Consumerist reports that due to a recent T-Mobile voicemail system change, iPhone users were unable to check their voicemail, and were being sent blank text messages when they tried to call in to check their messages, or when a new one arrived. One customer who…