Data disappearing

So about a month back I bought 1GB of data, which disappear literally within seconds of buying it. I wasn't even able to send a whatsapp message right after buying it. I sent a message to vodacom the same day and have yet to receive a response. The same thing happened today where after buying 1GB of data, it just disappeared. Really unimpressed with vodacom, especially since they're the most expensive and don't even bother replying to my message of complaint! Can't wait for my contract to finish.