KLM WHAT A NIGHTMARE

I booked 2 x flight tickets online on KLM - after the payment processed - the KLM website indicated "oops we have a system error" - I phoned, emailed, whatsapp KLM support to confirm that my tickets were infact booked - they supp**** a case nr and said I should communicate this to their agents - I tried for 3 hours to get help but the same message - they supp**** a phone nr - If you dial it - it indiacte the nr is no longer in use - finally I was told to go to their counter at the airport - via their whatsapp assistance they did confirm payment received. When I got to the airport the KLM desk informed me I have to pay AGAIN and the price increased with ZAR4200.00 - I have now paid twice and KLM is still not assisting me - or giving me my money back