Reception of Tmobile is not as great indoors as it is out door because they use higher MHZ thats 1900 most of the time and higher the MHZ its hard for the signal to penetrate inside building. And it also depends on the city, state where T-Mobile has a roaming contract with AT&T. Almost about 9 months ago T-Mobile still had a contract with Amerilink PCS and they dropped that due to which in rural area their service started to drop.
As you told that your co-workers service on your work zone sucks then you already know that you are not going to get any different coverage than them.
But let me tell you if your co-worker has Flex pay plan their coverage will be different than the regular 2yr contract coverage, which you get by signing a 2 yr contract with your approval credit.
I dont really understand what you mean by can you use data and voice.
Well when you sign up for the service you can choose between various types of minute plan and you can add unlimited web and messages for 34.99 for a smartphone and if you only need web it will be 24.99 for smartphone.