Disgusting service!

My parents are still waiting to get reimbursed for a claim from the 27th of July. I have posted a complaint previously and lots of emails back & forth but still waiting!!! With regards to my Son`s Lancet Lab tests from the 23rd of August I got Neurologist to write a motivational letter as they were related to his chronic condition and I see I have not been paid in full for this. Can someone please explain how this whole system works.