Major challenge deregistering from Milpark

I was unable to go through with my studies at Milpark due to visa reasons. I had paid my registration fees but when it became impossible for me to continue with the entire registration process, the staff agreed with my visa agent that they were going to refund me, I just had to email them my proof of payment and log a refund case on their platform. This was happening during Christmas time, hence I received an email that they will only look at my case when they open in January. When they finally opened, I followed up. The whole process of logging the case on their platform is so impossible that all the steps they said to follow were not available on the platform. I took screenshiots of this and emailed it to them. They helped me to log the case via email where I sent them the proof of payment and a form they gave me to fill out and my bank details as requested. After all this was successful, they told me to wait for 7 days for them to process the application. After a week, they sent an email that I did not have any amount on my account. I did not care for the money anymore because the process was taking long and it did not seem like they were going to send me the money but my shock came when they went ahead and registered me after they said I did not have any money on my account, which I'm wondering how they would register me without me having paid. I kept sending them emails asking them to deregister me as I had been requesting for a while now. They ignored me but have been sending me all the links to their classes. I have not joined any of them. They have been sending me emails, asking whether I am having troubles joing the classes but conveniently ignoring my emails about deregistration. Now they have sent me an email about payment overdue. I am so overwhelmed fighting them.