When it comes to cheap carriers, AT&T has its own "cheap line" in their "Pay as you go" product. I found I get all the benefits of their network at half the price of their subscriber line.
TG should include that in their tests. I used to be a Metro customer but in Dallas, TX, AT&T rules when it comes to speed and having a good signal or a signal at all. I pay $40 a month and get 10gbs of data with no throttling that I am aware of. So, I have my cake and eat it too with no deposit required, but I did have to buy my handset. I bought an Essential PH-1 anyway so I wouldn't be tied to any carrier nor suffer performance issues due to bloatware.