Poor customer service for contract holders

I signed a contract with cell c in July for a samsung A 31 that came with buds. I went to Samsubg to request my buds to be repaired and they requested me to get an invoice from Cell C. I called Friday and I was promised that I would have this sent to me via email. On monday I still did not receive anything. I called and as usual I spoke to 4 different agents who just kept me on hold with no response when I requested to speak to a supervisor I was told different stories

All I'm asking for is an INVOICE NOT A STATE MENT OR MY CONTRACT with the following to submit to Samsung as per their request * valid proof of payment to show that I purchased that I purchased my phone *The invoice must have my date of purchase of my cell phone *Cell C VAT registration *My cell phone purchased +IMEI I dont understand why must I be sent up and down