Tax Invoice Request:Flight Ref Number: NVEAZB

My journey started when I visited the SAA office at Wonderboom National Airport requesting the document and they couldn't help me and referred me to the Customer Service Centre. I have been asking for a tax invoice for the abovementioned flight for the past month. Please see South African Airways reference numbers: ********** 53608 dated 04 January 2018, ********** 64352 dated 12 January 2018, ********** 51602 dated 21 January 2018. Today I phoned the customer service call centre and held on for 41 minutes without the call even being answered. How difficult can this be to get a simple document e-mailed to me?