Bad claim service and not paid out the whole claim

I have logged a claim for house contents and the claim has been authorized. But only got paid 2 items out of 7 items because I was told when claiming that I am under insured. Something I was not aware of. When I was joining FNB insurance I was only asked of valuable contents not the whole contents. I had to call many times and send emails to the claim handler who did not bother to reply for the claim to be finalized. I have my car and my cellphone also insured with FNB and I wonder how they will treat me in future. The claim took the whole month. Every time I call there is a document that is waiting for managers approval. Really the worse experience ever since I clamed. I really don't understand why I was not paid the whole amount I claimed. And even if the people who ****** me took everything in the house, I wouldn't have proof of ownership for some Items as they are old