It started off with me filling out an application on their job website. You have also take a skills test at that time too. You'll answer some personality questions and navigate around a mock up of the software they would use for a Call Center CSR position. If they are interested in you they will call you and start the interview process. The interview process is fairly easy and quick. It started off with a phone interview by an internal recruiter. She asked general work experience questions and how my experience applied to this position. If the recruiter finds potential in you he/she will then schedule a face to face interview with you. My case was a little special because I am currently living far away from their call center. What would have been a face to face interview turned into another phone interview with two other recruiters. After that they decided whether they want you in for a 30 minute listening-in session and a final interview. (They do not hire you with out interviewing with you face to face first) The final interview was easy and listening on calls was great because you know right then and there if this is something for you or not. I personally liked it a lot. The overall culture at T-Mobile seems to be exciting and fun. There is a pretty thorough background check you have to pass. The company they outsource this to is called HireRight and they are a bunch of incompetent fools. Just work with them, in the end everything turned out fine and I got an offer which I accepted.
If you want me to be honest, don't waste your time applying for this job if you are not interested in taking an extremely high volume of calls on a daily basis, getting yelled at by strangers or being pushed to sell stuff to people. This position is solely based on performance. Experience is great but if you don't perform to standards you'll have a hard time enjoying this job.