Refund process at KLM Airlines

I booked flights in Oct 2019 for Amsterdam as it was a requirement prior to applying for a Shengen Visa and was advised by all agents at the airlines that the tickets i purchased are fully refundable should my visa get declined/denied. In Dec my visa was declined/denied and I contacted the airlines for my refund, the only refunded a portion of the amount that was paid, then when i queried it they now say that i need to give then a letter from the Visa office stating that the VISA WAS DECLINED/DENIED! why would they only refund a portion with the docs i had originally sent in and not the full amount of R18 257.86. Why do i have to provide a different denial letter when the refunded me a portion already. Is this how KLM makes money? they rob us of what we paid? there is no telephone number to call the refunds department you can only contact them via email and the turnaround time for a refund is up to 6 weeks, can you imagine how frustrating this is as the issue is ongoing since December.