wrong debit order going through my account

I got a message from altech saying I am owe them money only to find out that its my sister who's owing as they never changed her line so all her debt is reflecting on my name and now they took me to collection agent<br> Nudebt that says I owe them. I called and explained this to altech but it's still happening I am an unhappy client and I pay my contract on time.<br> Can they please sort this out as I always explain this to them....and this collecting company make unpaid debits in my acc and I end up owing the bank.