Penalty for no early upgrade!

I did do an upgrade online, recieved my invoice for this month and noticed I was penalized R1, 300+ for early termination (early upgrade) witch was not the case. I did check before and was eligible for upgrade on the 9th. Tried to solve with MTN, no success. Was put through to 5 different MTN yellow champions, nothing. Was holding on for another 10min,no one answered or assist.