Excuse me for my proposal but i have some doubts of the BHCA value. I wonder whether this value for BHCA is for BH or for all of call attempts made in your network?
I can’t imagine that BHCA can increase so rapidly, without corresponding augmentation of the subscribers.
Other approach for estimating TV:
From your post i understood that your DataBase have a field “TIMES OF CALL ATTEMPT”. Can you sum all values in the busy hour? The result will be the Traffic Volume carried by the network or the branch that you oversee in the Busy Hour.