Multichoice mobipay *****

I paid for my sister's dstv account using my fnb bank account and did an eft, we then contacted dstv to reconnect us, when we couldn't get through we discovered their whatsapp service and decided to use it, they sent us a link to make a payment of R29 that was short from our payment. They reconnected us, after that I have received 4 to 5 sms's from my bank showing that Multichoice mobipay is attempting to pay using my bank account luckily the OTP comes to my phone therefore they couldn't process the payments. I contacted Fnb ***** line but couldn't get through until I ran out of airtime, I then called Multichoice but they also said they could not help me. I tried again for the second time and got cut off because I ran out of airtime again trying to explain what was happening. I am very upset to have discovered that someone has my banking details and they are attempting to use it but no one can help me.