My housing complex is pissing me off. As you know we moved so last minute. We told the landlord we…

My housing complex is pissing me off. As you know we moved so last minute. We told the landlord we will be having a pet. She said fee is $400. We said okay. So some things came up and we haven't paid it yet so we have the dog by a family member until we pay it. But the landlord keeps rushing us to pay it saying we were supposed to pay it before we moved in. But why does it matter if the dog isn't even here? I could have told you no we not bringing a pet then a few months later brought the pet when we had the fees...so what the hell is the difference?