POOR SERVICE

I own an iPhone 11 Pro,which i bought on the 23 August 2021 through Pre Owned (SN DNPZ8A5FN6Y2 , IMEI *** ).It is been 2 months now since i updated my IOS and when i switch on the phone it showed no service!I have been running up and down ever since to get the phone checked with no luck!I was told that the phone was Blacklisted and had to go to the Police station for affidavit and go to my service provider,that was done and when i went to Cell C i was told that nothing was Blacklisted on their side,as my sim card is working,the Fault is with Apple.Went back to Apple but i cannot get help as my iPhone has a crack.....I DO NOT NEED MY PHONE FIXED BUT MY NETWORK!!TO DATE MY PHONE STILL DOES NOT WORK,HOW IS THIS MY PROBLEM IF THE PHONE IS BLACK LISTED!!***,WHY DO I HAVE TO SUFFER ALL THIS??