Unhappy customer

I have been a customer for more then 10 years and nou after a upgrade this year they debited to much I try to solve this Nd everytime I have to call in over and over again. June they took R1374 off my bank account which is to be R374. JULY THEY TOOK NOTHING. This month they took R1500 out of my debit orderfrom my bank. Now they told me it is a fault from there side but they don't solve their issues. What can to do now.