Sick of paying for wasted data

I purchased 600mb 7 day data and even received the sms to confirm it. I later decided to check my account balance and saw that my data that I purchased will expire in 3days even though I purchased a 7 day bundle.I called customer care and all they could tell was they sorry. I told her a out the sms confirmation and she was adamant I bought a 3 day bundle and that sometimes the system sends the incorrect sms out. She even admits the system can fail but insists I chose a 3 day bundle.I utterly angry because now im loosing out on 300mb that should have still lasted me for the week.She couldn't even try to fix it but instead said I should use all the data up tonight.What nonsense.I am hating this network each and everyday. I LOOSE WAY TOO MUCH MONEY WITH MTN. Its definitely time to change networks