I bought a used item of sportswear for my DD. Its very well known brand within the sport and has a reputation of running small.
The item was described as only been worn a max of 4 times as grown out quickly, no defects and immaculate.
DD has a few similar clothes of same make and fabric. I suspect the item has been washed at too high a temperature or washed a great many times more than 4. More importantly its tight 
. It should be roomy like DD's other clothes with the same size label.
DD is tiny. She weighs 5 stone and is nearly 12. The item is sized 12 -14 years.
The seller said no returns on original listing.
I know I should have looked earlier, the seller has only sold one other thing before. All the other many Ebay transactions have been as a buyer and has 100% positive feedback
What do I do? Contact the seller and try to reason with them or go straight to Ebay?