Phone Returned, ATT states not received

I've read quite a few posts about the return phones not being received by ATT.
I'm being charged $207 for my old phone that I sent out back in October.
I have the shipping receipt AND the tracking label that says it was delivered. Yet, ATT is still charging me.
I'm dumbfounded, I've been a mobile customer since 2007 and this is unacceptable.
we spoke to 2 different people st 2 different times, the first said there was no way to show whether they received it or not. The second one said we were good to go and that they had it. But they charged my account anyway.