Frustrated customer

i did an online purchase on the 4th of September 2024 , until now 26th of september i haven't received my order... they tell me the order was delivered , but me as a customer i am telling them i haven't received my order ....can they please cancel it and do a refund...They insist i received my order according to the last record on their system. and their system got hacked ..They don't even give you a courtesy call to explain whats happening and to keep you informed ....They don't pick up their calls .... Its taking them weeks to get proof that they delivered my order... They are not professional and have no respect for their customers. They reply on email whenever they feel like it