Cell C **** about promotion

I purchased a 5G data bundle from cell c off their app. I only bought this because I wanted to take advantage of a promotion they were running. Purchase 5G bundle and get canva pro for free for 3 months. But after I purchased I couldn't get access to canva so contacted cell c. Its been over one week and each time I call they couldn't help and said they were escalating matter. I've spoken to 3 persons calling me back. The last woman I spoke to said I can't access this because I bought it on a coupon and not on the app. However I did purchase on the app and paid directly from my bank account onto app. My bank records even reflect me making this payment. Again the agent said she will escalate the matter. This is not acceptable. I feel disgraced that they say I never paid for it and were insistant that I purchased it with a coupon. I will never purchase a promotion from cell c again. I want what I paid for and want this sorted out. I want 3 months canva and an appology for wrongfuly accusing me of not purchasing the way I needed to. I want canva 3 months starting the day they correct the error. David... ***