New Shipping label for my trade-in phone I had sent with the first label

I bought a new iphone with trade-in program, it was delivered on 2/7 with a return label in the box and the intructions how to return the old phone. Even 2 tapes to use to tape the box. I used this return label, and the box, sent my iphone 7 to att. Today, 8 days later, received a shipping label for my trade-in phone. Could you please explain why I received a second label and if there is any problem in this situation? 

Thanks,