Airtime disappearing even though I have data

1 September 2017 I got my monthly airtime. I bought a 1GB data bundle on 3 September 2017 and still had over R100 airtime left. Since then I've sent 7 sms's and made NO phone calls (I checked and counted). The rest of the time I go on Facebook and use Whatsapp. So big was my surprise when I checked my balance just now and saw that my airtime has decreased to R12.94, while my data is still 768.92 MB. How on EARTH did that happen? I'm seriously getting very tired very quickly with Vodacom. This is like the 3rd or 4th time this year I'm experiencing abnormal trouble with Vodacom. Don't know what's going on with you guys, but over R90 couldn't just disappear overnight. I made sure I bought a data bundle before my previous one was depleted. And I DON'T want your special extra data bundle thing that they phone me about every now and then, my budget doesn't allow for an increase in debit order. Please tell me where my money went to. I checked on the vlive website, and I'm not subscribed to anything that for example charges R2 per day or something. It tells me "You have 0 active Subscriptions". My patience is running thin. Fix this, please.