WAIT A MINUTE!
If the service was just done on the tranny, I would think that they should have SOME sort of obligation to warranty something....
They might be trying to cover up a problem. I have seen this many times on the dealer level. Just be careful and cover yourself...Not all things are done as deception, but this looks like it is in that category.
I would call MBNA first, then take it for a second opinion. It sounds like the fluid came out all at once, this happened to me once when a filter collapsed and sucked flat. It was a part failure, therefore I had to eat the repair. Not all work is profitable.
Be sure you know the CAUSE of the problem, not the result. That is how you will win.
ASE CERTIFIED MASTER AUTO TECHNICIAN
MERCEDES SPECIALIST 11 YRS