Failed to submit OSA subject

I am so disappointed with this institution, I received a email, whereas Mancosa informed me that my results is available. I immediately checked my Mancosa app that, just to see that it says I failed one module because I didn’t not submit my examination paper, which I did submit on the respective date and time frame. This is so disappointing and unexceptionable for a big institution to do this kind of fault, we as students are being taught to not make unnecessary mistakes but look at them now. I have proof of submission and it even shows on their portal so how can they tell me they can't see it. Their staff never answer their phones whenever we call, and our issues don't get resolved on time, can someone assist in this regard? I request for further investigation on this matter..it's the second time on the same subject which I had to re-register.

They trying to fool us by making more money out off poor people, people who are striving to better themselves in life and their situations.