My airtime is gone!

<p> </p> <p>About 2 months ago I loaded 30 rand airtime on my phone to do a sim swap.</p> <p>The simcard I was used was from 2004. This morning I tried to reply to a message from my mother and I had no airtime.</p> <p>This is unusual as I leave the airtime on my phone to keep MTN from closing the simcard. I only use a wifi connection on the phone and disable mobile data as all my apps run from the wifi.</p> <p>Getting in contact with MTN's call centre is not possible and from past experience, I am sure they will tell me I am subcribed with some mobile service provider that takes my airtime on a daily bassis. A service I DID NOT sign up for, so there is no way to get my airtime back.</p>