Can I transfer a t-mobile phone number to my t-mobile account (replace my existing number but use my contract)?

Yes, I'm asking another question again.

I try to transfer my contract to someone else.  And a girl told me she could use mine as long as she can have the same t-mobile phone number she's using now. Her contract is going to end soon, which just fits my time.

So, can I transfer a t-mobile phone number to my t-mobile account to replace my existing number but use my contract? I assume if the phone number porting is available, then this could be not impossible.

Thanks in advance!