Technically phone issue

Good afternoon

Please advise .I have a contract with cellc which is about 8 months old . I had a problem with my device Samsung galaxy A30s which in contract I was advised to take it to my nearest store which is ballistic lifestyle, I did and it was booked for repairs phone came back with no update as to what was wrong with it they only said warranty repair . After 4 days I recieved the phone only to find out that it is not fixed it still does the same problem so I need advise as to what must I do I am not happy with cellc . I am now stuck with phone that does not work properly and they refuse to give out loan phone when they send your phone for REPAIRs.whish to know what exactly did they fix on my device becouse it is still the same .

Thank you