Cell C
Incorrect Billing and allocation of Free minutes

I have a RBM200 contract which provides -
200 anytime minutes (= 3hr20min), 100 sms and 500 MB Data.

With reference to itemised billing - why am I not receiving my full 200 anytime minutes (3hr20min) usage, and at times not my full data either. With reference to my itemised billing:

Dec itemised billing:
I only used 2hr32min27s of free calls prior to been billed - the shortfall being 47min33s owed/ over charged.
I used 478.63mb of data, the shortfall of 21.369mb or 21882kb (using 1024kb per mb conversion).

Nov itemised billing:
I only used 2hr27min14s of free calls prior to been billed - the shortfall being 52min46s owed/ over charged.

Oct itemised billing:
I only used 2hr36min27s of free calls prior to been billed - the shortfall being 43min33s owed/ over charged.

Sep itemised billing:
I only used 2hr13min59s of free calls prior to been billed - the shortfall being 01hr06min01s owed/ over charged.

This continues for the whole term of the contract - incorrectly billed.

Please provide proof of used minutes if other than itemised billing. If contract as advertised is indeed different from billed, please provide proof of such.