Assigning a License

Please help! I do not understand assigning a license and I have been paying for Pro for a month without being able to use it. I try to add my name and it says I can't assign the license to myself? I'm the only one using it. I can't call because my account says it's Basic even though I pay for Pro. I have read the articles that tell you how to do it but I don't understand what they are saying. I'm so frustrated with Zoom that it is this difficult. I've spent hours and hours trying to figure it out. Thank you for your assistance!!