It sounds as if you feel frustrated. I can certainly understand your frustration. You have spent a lot of money and time; you have also worked hard and have not yet received your certificate. I agree with you that it was wrong to announce your result to your classmates.
You are right to say that if you have barely passed, you have still passed. I would start by contacting the training centre and trying to find an amicable solution. Can you go in to see them or phone them? It could be that the certificates have not been sent out yet – you could check this with others who were on the course. It is also possible that the certificate has been held up in the post. In any case, contact the training centre to find out what is happening.
If this approach doesn’t work, you can consider other options. However, I don’t think it is right to ask for a refund. You paid for the training, materials, etc and you definitely received this.
Good luck and best wishes,