*****ing airtime!! Extremely upset

I had a balance of R40 that I owed on my airtime advance. Yesterday I recharged with R48 through FNB Ewallet. I checked my balance straight after and it showed R8. I was unable to take an advance again and bought a 25mb boost bundle with the R8. About an hour later I was able to get through to my advance balance. It showed I still owe R38 and only paid R3!!!!!!! How the hell!!! I called customer care and send a facebook message! No one can help me so far! So what happened to my R38.????? I could only take R2 advance this morning. I want my R38 that was loaded and deducted!! Im very dissapointed in Cell C