Complaint for service centre laxmi nagar

I have given my laptop to  laxmi nagar service centre around 14 june for diagnose my issue with laptop the say it have mother board issue so i have to pay 12003 rs to dell  account  and i have paid last to last  week on Saturday 21 june    after i tell them i have  paid and send them screenshot of the payment now i have inquired about the laptop  they say you need to send them a bank statement  and don't even given invoice  for my payment