How can I unlock IMEI

According to that screenshot, the issue is not that the device is locked to a carrier. The issue is that the device was reported stolen to a cellphone carrier (Not necessarily T-Mobile). You will need to contact the person that sold this device to you. If they are the original owner, they may be able to get that block removed the same way they placed the block in the first place. Your best bet would be to return the device to them and get your money back.