I got my first ever freelance job. I finished the work, but I'm not sure if my client will pay me.

How do I know if my client is going to pay?<br><br>To throw out all of the details:<br><br>I get my first job on Fiverr. The client said they had a project that needed to be completed. They told me to work on it. They didn't pay me a cent before I got work. I told them that I was a new seller, and they were to pay me first. They got mad at me and told me to give them the final answer. I did, and they never replied. Then, they did, after a day and said they were going to need me and that they were sorry.<br><br>They said they were going to pay me after the project was finished and that they would pay the whole price. I finished the work. I gave them an invoice and they haven't replied yet.<br><br>They said they were going to pay when the project was finished, but I don't know if they are going to pay me or not.<br><br>What should I do?<br><br>&#x200B;<br><br>TL;DR : I got my first ever freelance job. I finished the work, but I'm not sure if my client will pay me.