I need to get my iPhone unlocked from the network T-Mobile, they said they need you to do it

1. We, the readers of your post, are not Apple employees. We are members of this Apple community just like you are and try to help each other.
2. The T-Mobile representative did not tell you the truth. Call T-Mobile support again and ask them for the procedure and requirements to get your phone unlocked. Only your carrier (T-Mobile in your example) can unlock your phone for use with other carriers.

Axel F.

T-Mobile is generally very good about unlocking phones. You just need to speak to the right T-Mobile support rep. Do it over the phone with tech support rather than with a store, as the stores only have salespeople these days.

Only the carrier may unlock the iPhone if they choose to do so. Read and follow the article linked above.