My telkom billing is fictitious and inflated do something about this

My telkom billing for march data usage is fictitious and inflated. My telkom bill for usage of February showed that I had exceeded by 12.3GB resulted in R165.70 extra charges. I went to a local telkom store and was told dial*180 option G and spent limit R1.0; I stopped exceeding my contract data amount in the February. Surprise now my march month data usage shows that I have exceeded contract amount (despite stop exceedeing) by 12.9GB. I had stopped exceed amount by following above process how comes that my data usage was still exceeded by 12.9GB and I have been billed an amount R 526.08. Second concern is this amount looks quite suspicious and inflated and fictitious. All these does not add up first if I have stopped exceeding data usage how come the bill shows that I exceeded and the amount charged looks highly inflated. Telkom could respond to this matter with view to resolving this irregularity that is quite blatant