I'm sorry to hear that you are facing this type of bad experience. I suggest you please communicate with the buyer and talk details. Try to understand what your buyer needs and fulfill his/her requirements. Best of luck.
This is a tricky issue, but it's challenging to convey the problem. Unfortunately, there's no straightforward solution. However, you can explain the limitation to the buyer and suggest placing a small order (like $5) to address it.
Fiverr allows multiple users to have separate profiles on the same internet connection, as long as they are different people offering distinct services. It's straightforward.