Empathy will go along way in this situation. You are both at fault but the client is the customer, so as a business person you need to decide how you handle that.
Enter a negotiation with your client, accept that you should've agreed terms and offer them a discount based on that, its very important you be respectful and don't get entrenched in negativity.
Simply accept you should've agreed terms before the work started and because of that oversight offer them a discount and go from there.
If the client is disrespectful to you, drop em and move on , but drop them respectfully.
Empathy will go along way in this situation. You are both at fault but the client is the customer, so as a business person you need to decide how you handle that.
Enter a negotiation with your client, accept that you should've agreed terms and offer them a discount based on that, its very important you be respectful and don't get entrenched in negativity.
Simply accept you should've agreed terms before the work started and because of that oversight offer them a discount and go from there.
If the client is disrespectful to you, drop em and move on , but drop them respectfully.