iStore Menlyn terrible after sales service

iStore Menlyn admin issues!! Quick to swipe your card and take your money, but slow to respond and rectify anything that needs to be corrected. I purchased a Macbook pro in May for my business. Unfortunately I have two profiles at the iStore that use the same phone number (one for my personal account and one for my business). On the day of purchase I gave my phone number, they looked up my profile and proceeded to swipe my business card for the purchase. After the purchase I realised that they used my personal profile instead of the business profile. A few days later, I returned to get a VAT invoice from the store, which I need for accounting and tax purposes. The sales person took down my details and mentioned that the manager would be able to do this and email me a copy a little later. After a week or more of not hearing anything back from them, I had to go to Menlyn again in order to find out what was going on (seeing as there's no other way to contact them directly).

Now I am told that they are not willing to re-issue an invoice to me as it would affect my Warranty. They can back date the invoice for all I care, I don't need an extended warranty, I am quite happy with the item I purchased and I believe that I won't have to use my warranty in any regard. I just need a simple re-print of an invoice with my correct details, surely that cannot be so difficult. It should be a small correction seeing I just spent R40k at their store.