OPPO Phone have factory fault.

I bought OPPO A78 on the 24th march 2023,on the 29th march I took it back to the store and they checked it and it was fine."i don't know what they did". On the 4th of April 2023 I took it back again with the same problem and the manager suggested that it must taken in for repair,bare is mind the cell phone is 11 days new.

They took for repair on 17 April 2023 and it came back around The 15th May 2023 and report says

"Fault Description was 28 SW Application Problem Action Description 5 software Upgrade "

Just 3 days later the same problem started, am now stucked with the Oppo that is malfunctioning which is now 4 months old and still paying for it every month. Am so angry and frustrated with this oppo fone that can't be fixed. This fone have factory fault can Oppo South Africa do something about my problem?