Can't use my phone despite having airtime

This morning I had some airtime and data but when I tried to make calls I was told that I have insufficient airtime. When I attempt to access the internet same thing happens and two hours later I checked my balance it 0.00. What annoys me is that this isn't the first time and I am tired of it. What happened to my airtime and data when I couldn't use them. I have loaded airtime again and i still can't accesss the internet. I called 173 and couldn't get through, 808 my call was cut what am I supposed to do now? Leave the network? Please advise as I can not take this anymore