Voucher can't be loaded but it's NOT A PROBLEM

After repeatedly phoning MTN (around 40 times on their 173 number) with the line either dropping or being routed to some woman with an American woman who wanted me to place an overseas call, I managed to speak to three people who variously tried to reset my phone, load my voucher themselves and direct me to try 555 instead of 141 (to load the voucher). I was told there was 'no problem' with the voucher but I should go back to the store where I bought it and get a refund. I have tried that before (oh yes, this HAS happened before) with no luck. It was virtually impossible to speak to a human