Because attacking your competition in the media looks really good to consumers.
I'd shy away from them just because of their ad stance.
If it benefits the consumers in the end (aka rates going down & improve service) and ad being truthful, let them fight in their ads.
I have no problems Samsung & Microsoft attacking Apple for as long as it is truthful and force Apple to improve / not too be complacent.
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Okay, then allow me to amend that poster's statement:
For me personally in the Washington, DC area: T-Mobile's service indoors is utter crap. It is almost nonexistent - as if a cell phone only works outside. Sprint, AT&T, and Verizon all work indoors in most buildings.
I'm a real estate agent who shows a lot of houses throughout the year, so I have the opportunity of being inside a lot of different buildings. Yeah, T-Mobile inside is crap.
For me, a God-awful, cringe-worthy, business-halting network. For you, if it works, T-Mobile is a great deal. Go for it! That's why they have test periods/return policies.
However, if you live in Washington, DC or the surrounding areas: you better love WiFi calling.
Fairer point now.
With current AT&T's (with or without contract) charging rates / plans, it should be perfect.