Stuck on this one - any advice welcome

I ordered something from abroad - total value £95 including shipping. Received a grey slip from Royal Mail saying there was a customs charge which I paid immediately and have the confirmation email with receipt and the confirmed date they would deliver. Since then the package simply hasn’t arrived - I’ve called the delivery office 3 times and they keep saying they will deliver on a given date but it’s never delivered. I’ve been waiting over a month now, and to make matters worse, now when I call them I wait in a queue for generally between 20mins before they just cut the call.

Has anyone else been in this situation? Should I go down to the delivery office and pick it up from there in person (bit out of the way so it would be a pain but I’m at a loss what else to do)

At what point do I write off the package and try to seek compensation - and does anyone know the process for this or contact details for RM legal team?

Thanks in advance for any thoughts - really at a loss on this one