Bad service

I opened a account with Lewis in October there manager put my debit order for a wrong amount I inform3d them in November no one came back to me now they want to come and say I am sort on my installment this is very bad I don't think I want the product anymore they made the mistake now it look like I was at fault.i did inform the consultant to inform there manager to call my she did not call.now they want to come this is the wors service every