Refusing to pay after pre approval!

I have been pulling my hair out trying to get money back from discovery! Healthcare providers request that we pay upfront and we claim back from them and I now understand why! They will delay payment and push you from pillar to post!!! So disappointed I’ve been having issues with numerous claims. I email the claim and get a reply with a reference number and that they will process in 2-3 Working day. I call a week later and am told that the claim has never been opened! And I must now wait another 2-3 working days! Bear in mind this has happened more than once

The more pressing issue is that they had pre approved therapy sessions after a stroke and when I claimed they keep rejecting! I’m trying for a month to get it sorted and each time I phone there’s another excuse and they promise to attend and process within 2-3 working days. I have spoke to about 4 consultants about this! For over a month ! And still no results ! Or explanations! I’m just so frustrated