Just go to any Tmobile store for a replacement. While you could get one mailed to you by calling customer support, store is more convenient if you have one close by.

The SIM does not control the phone number. That’s an entry in a database. You just need to get a replacement SIM and have it activated in place of the one you lost. Unfortunately, T-Mobile won’t ship SIMs overseas, so you’ll have to wait until you get home. Either that or have someone forward it to you.

I just opened an account with T-mobile and the sim card they sent me is not connecting.  I cannot use my phone to call, or go to a physical location. I wlike to have an e sim card set up on my phone. Why doesn't T- Mobile have a chat????

it says no sim card cant call or text

helo iam from djibouti i pay phone oneplus 9 5g and is locked sim i try to unlock  but is show me is not eligible how can unlock the sim card please

You need to be a customer of Tmobile USA and meet the requirements in the link below to be eligible for an unlock code.

https://www.t-mobile.com/responsibility/consumer-info/policies/sim-unlock-policy