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I have a number of unlocked devices on T-Mobile service with any issue. They do not block phones that are not theirs. It is possible that the bands your phone supports are not in service with T-Mobile. What is the model number on the phone you are trying to use?
hanks for your reply. My phone model is "redmi note 5-global version" which I attached the supported LTE band as follow. Regarding to my investigation my device has no issue with LTE internet service but for VoLTE it is required device provision by its IMEI. I have tested Nexus 5x which was on same frequency band( Number 4) with same tower coverage(using LTE coverage monitoring android app) had VoLTE but mine has not.(two phone called each other!)
As long as I understand T-mobile suggested me to switch my phone to another T-mobile supported device and it is not the best solution. I am wondering if anybody have same problem/issue on the unlocked device or not.