Completed studies, but no stamped documents and the graduations department ignoring us!

I have recently completed my PGCE with Stadio DL and received my academic statement on the 18th of Dec. I noticed that they've recorded a wrong ID number, and it didn't indicate that my studies were completed. I tried reaching out, with no avail. They next sent a completion letter on the 6th of Jan, still with a wrong ID no. plus no stamp again. For a reputable institution, I believe they should by now know that we need a school stamp on such documents. I tried reaching out on email and calls since the 6th of Jan, but still got automated replies and was transferred to any other department except for the graduations one. I've already missed a deadline for 2 job opportunities because I can't apply to SACE with incorrect and outstanding documents. It's so disappointing and frustrating how nobody cares about us, the DL students at Stadio!