Airtime disappearing

When ever I recharge I make sure that my data is switch of so that my airtime does not get consumed by the internet, today I did the same process and recharged with R12 and when I checked my account it said R8 when I called in the told me about the subscription and when I told them that I don't have any they told me that the airtime is still the all I need is to switch my device off then on again only to find out that my airtime is still not back and I called in again they took my information and hanged up on me this is not the first this airtime thing happened I am tired of it, I was planning on upgrading my device but with the service they give of late it does not look like I will with them