Ridiculous service so far

I and my wife bought mini tablet phone brand Alcatel at vodacom Makro wonderboom cost of the tablet was R799 as it was on promotion less than 3 months I discover whenever the tablet is fully charged 100% in less than 5 minutes the battery goes flat. I booked the tablet in at makro wonderboom for repair noting the phone after been charged 100% battery doesn't last 5 minutes. After few weeks I was called and informed the tablet can't be fixed it will be replace with a Demo one and I was quoted R950 for the replacement which I declined and informed them to return back the tablet to me. Upon receiving the tablet I discovered the tablet doesn't charge at all anymore it blinks while charging and doesn't power on at all anymore. This is totally unacceptable and horrible service. I don't understand why the tablet can't be replaced under warranty how ever if can't be replaced vodacom + makro must return the tablet back to me how I gave them before booking it in for repair.