Strange T-Mobile Behavior My LTE smartphone supports frequencies shown at the bottom of this message. I have been using this phone without issues on T-mobile for about 3 years but last month or so I noticed that LTE switches to Edge when I receive an incoming call. Ditto when making an outgoing call. As a result, I lose internet when a call is active. If I drive 10 miles away to the next city then phone's behavior changes. In that city, LTE switches to 3G/HSPA+ whenever there is a call active so I can keep the internet while making the call.

Did anyone else see similar symptoms on their phone? Any ideas if T-mobile might have "out-frequencied" my phone in my city?

My phone supports following: -

GSM: 850, 900, 1800 and 1900 MHz; Bands: 1/2/4/5/8

3G: 850, 900, 1700, 1900 and 2100 MHz

LTE: 700, 1700, 1800, 2100, 2300 and 2600 MHz; Bands: 1/3/4/7/17/38/40

VoLTE: Not supported by my phone

Update 1: Just to clarify my question - I expect my phone to switch from LTE to 3G/HSPA+ when a call is active. But unfortunately, it is going from LTE to Edge in my city. Why?
I do believe that is called csfb (circuit switched fallback) here is my source http://www.telecomabc.com/c/csfb.html