Price lock wrongfully charged - over charged

I signed up for a price lock last Dec 2018. I have been over charged several times. I have called the call centre multiple times and all they say is they will get back to me within 24 hours. I have also contacted them via Twitter and they told me that they have sent the matter to the Price lock department. It's been over 2 weeks since I have contacted them. It seems that they have changed my package without consulting with me 1st because even the amount due at month end shows a normal premium package instead of price lock. This is not the 1st time that Dstv has overcharged me on this price lock deal. They seem not to care about their customers.