Are these 2 fluids not compatible?
The T-IV is a 7.5 cSt viscosity fluid while the WS is a fuel conserving 6.0 cSt fluid similar to DexronVI. The WS has better cold temp operation, better oxidation resistance, and better friction modifier retention.
I doubt you'll have any damage and as someone else stated, you got a good tranny flush and maybe the dealer will be more careful.
Does the receipt show WS on the ticket and did you see them put in the WS?