MTN does it again

What is going on with MTN. I am so sick and tired of having to fight with MTN. I have caught them out on several occasions Overcharging roaming calls and sms'. In January I sent a company Letter before leaving for Namibia requesting them to deactivate roaming Voicemail. Apparently they didn't receive the letter. MWEB confirmed that my email to MTN went through successfully - thus the problem was with MTN. At the time I was unaware that I was supposed to receive an automated reply. Subsequently they charged me for roaming Voicemail. when I returned I logged a dispute. The lady I spoke to was extremely arrogant and refused to listen carefully to what I explained. Eventually I re-sent the Letter and decided to pay the portion of the Invoice minus the roaming cost. And guess what. Typically they closed the matter as being resolved and typically they suspended my line. By law they have no right to do so as I did make a payment. Also do I still have a Balance of 84 anytime minutes that are already PAID for. So legally I could sue them as they took away "property" that is not theirs. Or in another way one can say they are holding my available minutes ransom in order to force me to pay for the roaming fees they were not supposed to let through. How much more must happen before MTN comes right? Maybe it's time they get another huge fine for their irregular billing... Although the amounts are small I can prove that they overcharged on several occasions. Also do they not clearly indicate which numbers called that left Voicemails - so there is no transparency. MTN need to get their act together. With software capabilities they could easily automate the Voicemail Service to be deactivated once a SIM Card is out of the country - but they try and hide behind ignorance in order to ***** us over. How many other people just pay because they are even more sick and tired of fighting for what is right?