How does T-Mobile make decisions around promotions?

There are a few pathways to promotions. One is the VOT process ("Valuing Our Talent") which is an HR program for management to issue raises and to promote employees. Each department is given only a few (like 1-2) spots per year for promoting employees, similarly, there is a dollar amount provided for raises. These spots are hotly contested within departments. If a manager really wants to promote an employee and VOT is not a possibility, they can repurpose an open position. It works like this: employee A should be promoted, so their manager has them apply for an open job that also reports to that manager. Employee A gets a pass-through interview process and promoted to the new level. The manager then opens a backfill position for the original role. The last way to get promoted to apply for another job within the company. Roles (at least in technology) go: Product Engineer > Senior Engineer > Principal Engineer > Member of Technical Staff. Each bump is at least 5 years.

I just asked my manager for a promotion after a few months and he agreed. I got hired as a mid level motion designer, that's what the position was, but going in I was already senior level based on my years of experience and skill set. After a few months, and seeing everyone's work and finding out other senior team member's experience and skills were lower than mine, it was obvious I am the most experienced and skilled person on the team. The senior members on the team even kept saying outright to my manager and to me that if they're senior, I should be director. So, I asked for a promotion after a few months and just got one. In my case, they just hired someone overqualified for a lower level position and T-Mobile listens and understands, so I got promoted.

You have to identify what you want to be and make a plan to get their if you want to promote in place otherwise you just apply for roles your interested in

It is all based on performance and ability to adhere to T-Moble competencies.