Useless bank

There was a transaction made on my account on the 24th Nov 2017which I wasn't aware of and I've noticed it on Monday then I went to the bank on Wednesday to report it. They said they can't reverse the money without that person's consent which they tried to call him but seems like his phone was off. I waited for 8 days they never called. I called them they said I should open up a case ,how do I open up a case isn't this their problem to sort it out n gimme back my money? First of all I don't know the person....I thought our money were safe in these banks but clearly was wrong,better safe under the mattress at home