Prepaid recharge

Unexplainable depletion of recharged airtime. I am a high volume user and lately my airtime is being depleted faster than my normal usage. This morning I recharged with R180, made less than 10 calls all under a minute and now I get a message that airtime is insufficient. Called the call center and I'm told their system has not updated since around 12pm. The highest usage recently recorded when the system updated is approximately R50 internet usage, but at this time I was in the office using wifi connection. I do not understand if the system has not updated how is possible that it can detect that I have exhausted the funds. My data has been depleting at a faster rate as well and I strongly believe there is a problem that mtn is not detecting on their system or they are just blindly ignoring. I need mtn to own up and explain in detail what is going on with their system or else I'm going to stop using their network.