I sympathise with you entirely. I have a severe stutter. My priority for calls where I do not know everyone is to introduce myself as a stutterer. If I try to hide the stutter, everything becomes worse. I now join and take calls every day at work. It is difficult and sometimes I don’t want to participate but I force myself to and my contributions are respected. Despite my stutter I have progressively advanced my career and discovered that the main thing that holds me back is myself. When I was 17/18 I didn’t pick up the phone and it became a prison for me. I forced myself to work on it. I called random stores to find out when they closed as practice. If they hung up I called back. I asked about products, I used phone lines for services I have rather than doing it online for the practice.. It helped with my confidence and while I was always far from fluent I became more understandable. I would encourage you to try to take that step. I would encourage you to call the art school. Most institutions are very helpful when it comes to disabilities, I am sure they will be supportive. I don’t know how far it is but perhaps you could visit in person if the phone is a problem and just be open about your struggle and what has happened. There is nothing to lose and everything to gain.