Trade-in question

We switch to T-Mobile yesterday. 

One of our phones has a cracked back but there is NO water damage and the phone works perfectly well.  We were told in the store this phone would be accepted as a trade-in for a new phone because, and I quote, “that is T-Mobile’s policy”. 

So we all got the Apple IPhone 12 promotion ($830 off over 24 months with a trade-in) except for one of our lines - he got the SE so 100% off over 24 months with NO trade-in so we just traded his in for a bill credit.   Apparently we should not have done this because…...

We were told since we were sending her phone directly to her at college, it would be easier to just order it ourselves.  So, last night, I was chatting with someone online having her place my order, very nice lady named Bea.  But she told me we could not trade in the phone because of the crack - therefore not getting the same Apple iPhone 12 promotion.  So now basically, we are out quite a bit of money.

Were we told incorrect info in the store?  Was I told incorrect info in the chat about it not being accepted?  Is there anything I can do now???  I haven’t placed the order yet...