Bad customer service from Post Office

I need an urgent document sent from the UK during Sept 2020 that arrived on 16 Oct in the department in OR Thambo. I have made 6 calls to stress the urgency and sent 5 emails to the 4 applicable email addresses including VIP Service. No on bother to reply to my emails. It is an original title deed which we needed to lodge to the deeds office and now the whole deal collapsed. I am considering a claim towards the Post Office