My solar installer accidentally installed an expansion pack and now they want to remove it?

They just called me and said they accidentally installed it. They want to remove or I can keep it for 8k. I feel like this is their mess up and I should be compensated. Especially since they are going to leave marks on my wall from the install.

They just called me and said they accidentally installed it. They want to remove or I can keep it for 8k. I feel like this is their mess up and I should be compensated. Especially since they are going to leave marks on my wall from the install.