MTN APP purchases of airtime disappear

Guys pleased help. I'm a new MTN customer. Did you your call centre simply hangs up the call as soon as as I mention I have a problem with your app. If I buy airtime it simply disappears. I'm unemployed and that's a lot of money to loose. It's now 6:24 in the morning. Second time I speak to the same lady. She simply says hello, hello the whole time as if she can't hear me. I called my housemate who is also awake early and he can hear me. I've reinstalled the app several times and cleared the cash and it simply doesn't work m