Airtime disappear/gone

<p>I loaded R20.00 MTN airtime Saturday afternoon and when i tried to make a call then it was said i had insufficient airtime to make a call. i restarted my phone and then only R8.07 was returned which i still couldn'n use now it has been R0.00 since. i'm tired of complaining about poor MTN Services but it seems not to improve...</p>