Why pay for DSTV Disney subscription error

End of December 2023 DSTV deduction form my account was not correct - R139 overcharged. After checking invoice DSTV added Disney plus without any consent or request from me. I then saw they credited my account, BUT the credit was for R121,06 so this means that i paid R18,94 for their mistake. What bugs me is the thought of all the R18's that they have made profit, straight bottom line, what if they overcharged 1 million people , that is R20 million rands, I also want to do business like this. We would never know how many people was overcharged. I just want my money back plus interest and again a BUT - to call DSTV and sort this out the call queue will cost more than R18. Surely this is ***** ?? please correct me if i am wrong. DSTV please tell us how many people is charged R18 for your error, was this planned or a real error ?