Cellc Cavendish square OBF inconvenient

Please help me I bought a Samsung A3 core at the cell branch in Cavendish square shop on the 6 April 2021 and after having the phone for 2 days it starting rebooting it's self on it own it was a brand new phone that I payed cash for which was R1299 at that branch and to my understanding falls under the OBF warranty period when going back to the branch I was told that I will have to book the device in for repairs and have to wait for feedback on from repair centre.I have no phone that I payed cash for and also have to wait.cellc you have really inconvenient me because I payed for a phone and now still have to wait for it to return.i don't want that phone no longer and would like to have a other device or a refund on my money asap.you cannot inconvenient customer like this.