I am having this same issue. I went on a job interview and was told to expect a call on Monday 8/20/12. Today, 8/28/12, I get a beep that I have voicemail. I have been checking all week and nothing but today I have a voicemail from the job and when I checked the details about the message it was sent last Monday. I have put in a call to them and hope I can still be considered but this is absolutely ridiculous and I am giving serious consideration to cancelling my service. Not to mention that in the last 2 months my coverage has gone from the entirity of my front yard to a roving 3 foot by 3 foot section that is never the same place twice. I originally has such good service that I got rid of my land line but just last month had to have a land line put back in because I cannot get calls at home anymore. Often times my text and picture messages are delayed by as long as a week, people can call my phone and I can hear them but they can't hear me or vice versa, and calls drop for no reason. All of this has occurred in the course of the last two months and when I call in to TMobile for assistance I get stuck on the phone with someone who barely speaks English and is usually down right hateful.
Sorry I don't have an answer for you but maybe it helps to know you are not alone.