theft by overpayment

i make regular payments to dstv every month as the amount displayed instore or via my capitec app.Today i paid the amount displayed on my w.app and low and behold dstv decides that i owe them 1200 and they block my acvount,i tried making contact on multiple platforms but it was to no avail.The customer service is just as poor to begin with.I am really sorry but i will cancely subscription after almost 10 years of being with them,ive never had any troubles before