I have registered with Intec college for a short course I submitted my assignment and that was it , they don’t get back to me, they listed me on credit bureau , I paid but no certificate, no paid up letter, I call them every day and I can’t get assisted

I have registered with Intec college for a short course I submitted my assignment and that was it , they don’t get back to me, they listed me on credit bureau , I paid but no certificate, no paid up letter, I call them every day and I can’t get assisted I need help to get my certificate and also a paid up letter as this affect my credit score