Broken Tablet sold as new!

I bought a tablet for my daughter. This worked only a month and I just put it away as it was not for emergency use. I later took it back for repairing as it was only switching on then would be blank. I was told this takes 14 - 21 days. Indeed I received an sms to go collect, when I got there, nothing was done and the staff didn't know, just that it's the other department and there is nothing they can do. They just advised that I have to wait 21 days this time, with no guarantee that things will go well. This is really not a good service at all. One staff member even advised that I can take it somewhere else as he believed the problem is programming. I need this to be fixed or have my refund. This is really not a good service. This means the goods sold are not in good condition, considering all these queries.