My issue is similar to other threads I have seen here. I am a on a grandfathered Simple Choice NA plan with 10 GB of high speed data. I am not close to using all of my data. My data speeds are always around 10 Mbps (or higher) download and 8 Mbps upload directly on my phone. (On the SpeedTest I just ran I got 25.5 download and 8.11 upload.) However, when I USB tether to my laptop (or desktop), data speeds drop to about 0.3 Mbps download and 0.1 Mbps upload.
I have multiple lines with T-Mobile and multiple phones. It happens on all phones and all lines. The issue is not related to my location because data speeds on the phone are adequate. As soon as I USB tether, speeds drop drastically. The issue is not related to tethering to one particular laptop either. I have been having this issue for the last 1.5 years and in that time I have used several different laptops. Prior to 1.5 years ago, tethering speeds were fantastic. My T-Mobile plan has not changed during this time.
My phones include a Galaxy S8 and a Galaxy S8+ (but the problem has happened with prior phones, as I mentioned). My phones are all T-Mobile branded devices. My current laptop is a Lenovo ThinkPad. I do not have to use a 3rd party app on my phone (USB tethering is built in to Android on the S8, S8+) and I do not need a 3rd party app on my laptop. When I turn on USB tethering, I get a proper connection. The issue is that it is very SLOW.
I also tested the mobile HotSpot feature. For about the first 5-10 minutes, I had good speeds while connected with my laptop, but then the speeds dropped to the 0.2 or 0.3 Mbps range and stayed there the rest of the day. That looks like throttling to me...
Over the last 1.5 years I have called T-Mobile support many times regarding this issue. Tickets have been opened. Unfortunately, no solution. Usually the support person is very nice and promises to follow up with me. So far not a single person who has made me that promise has actually followed up.
Multiple T-Mobile support reps have told me that my plan has no throttling of my 10 GB data allotment. I used to be a huge T-Mobile fan. I have had my current account for over 6 years with multiple lines. Before that I was with Verizon for 2 years, but prior to Verizon I was also with T-Mobile a long time. (I was a loyal T-Mobile customer even when their network was not as competitive as it is now.)
Can anyone from T-Mobile solve this for me?