[How can I increase Price and modify delivery date on an active order?]

Dear all,

I am a fairly new user and landed my first order. However, my buyer requested I speed up the delivery by a few days and offered to pay additional charges. Please help me figure out how to modify the price and delivery date of my active order, if any, or suggest to me all other ways to go about it.

I appreciate any and all inputs, thank you in advance.

- Dishani