Ordered incorrect Apple Watch strap size 40mm instead 49mm as I have Apple Watch ultra

I have done purchase of AirPods Pro 3 along with Apple Watch strap 40mm. after placed the order I have realised that the strap size won't fit to my current existing Apple Watch Ultra. Now I am seeking help to exchange the strap of 40mm with 46/49mm which best suites my Apple Watch. And the order is still "Processing to ship only" but no luck in exchange. Is there a solution for this ?