HTC Sensation from MTS?

Question

HTC

I ask knowledgeable people to explain, because I do not understand anything. A colleague bought an HTC Sensation with the MTS logo. As I thought, this means that the phone only works with MTS. But in practice, she calmly stuck a Beeline SIM card. At the same time, the phone works somehow strangely: it calls, receives SMS without problems. The Internet stubbornly refused to go out. I manually configured the Beeline access point. The Internet began to periodically turn on for a couple of seconds and disappear.
Also, according to her, the phone does not see Wifi at her place. Laptops work without problems, but the phone does not see.
Some applications are buggy (for example, after launching the repeater cat, after a few seconds of use, the sound disappears, moreover, in the entire phone).
The question is, what could it be? Glitchy device? Such a reaction to a non-MTS SIM card? Or something else?

Answer 1

Try to work with the device without a SIM card. if problems with wifi and sound are repeated, then the problem is in the device

Answer 2

In vain they bought MTSny. There is no official firmware update on them and, most likely, there will not be. The firmware there is the very first and most buggy.