Help please!! I used the free trial of Trello Premium and now I'd like to purchase a one year subscription. As part of a public school system, we are tax exempt. I was told to "upload your certificate by clicking the tax exemption button under the billing tab" but I don't see a billing tab let alone a space to upload the form. I'm so frustrated! All trello customer service will respond with is the same auto response that they've previously provided.