Missing money

<p>To who it may concirn.</p> <p>When I made a call this morning it said that I had less than R3,99 in my account...fine because I don't use money to make a phone call...I pay every month for minutes. During my call I was disconected. When trying to make a call again it said that my airtime was finished.I checked my balance.the remaining airtime was finished but I still had plenty of minutes left on my balance.</p> <p>So,do I pay for minutes every month but still pay for every call I make as well???</p>