Poor service

I received a faulty Dell tablet which kept turning off and resetting itself. I then went to Dion Wired in Boksburg and spoke to Shafiek, he advised that the software was outdated and needed to be updated, so he had the device cleared and I then took it home and started again to check if it would continue, which it did. I then reported it to him and he said he would arrange for a technician to collect it. I then spoke to him last week to find out when the unit will be ready and he informed that it would be ready by Tuesday this week. I then phoned to find out what was happening and i was informed that the unit had only been collected today and that it states on the service slip that it takes 21 working days, I never received a service slip. I either want my unit back before close of business tomorrow the 20-05-2015 or I want a refund and I will take my business else where because you clearly do not need it.