TFG **** PROMISES AND LIES!

I ordered a dress from Donna online, it came without the chain around the neck and I requested a return. The following day i was expecting a courier from them and another from Adidas. So, when the courier guy came i explained that i had two items and asked which he was there for and he said the Adidas one. Later on it turned out he was from TFG but he picked the wrong item. I then called TFG to explain and they agreed to return the incorrect item and take the correct one, but they only came for the dress and til today i have not received my item from the Adidas store. Whenever i phone them the consultants put me on hold to call the warehouse then promise they'll get back to me but they NEVER do. I'm just sick of this. What does one do in this case? get legal advice on the matter? Its been a month now and obviously i won't be able to return the item to the Adidas store anymore! Their customer service is pathetic but i won't give up on this. I want my item!!!