Hello I did some work for someone and did not get paid. The reason they are refusing to pay is they say services were not as described. While I agree that services were not 100% as described, I believe they were 80% as described and not paying anything at all is not justified. I have a contract that says they have to pay for all court costs and attorney fees and all other costs relating to collections. I am not going to get into details regarding all the fights I have had with them over email. I just have a very quick question. Should I send an invoice through the mail, and wait one week, and then send a demand letter advising them that i will be suing, or should I forget about the invoice and just send a demand letter?