Horrific state of claims department and it's service

On 29 November 2017 I submitted several claims (all original statements with receipts that payments were done) all in one envelope to the claims department. The department was processing one (!) out of 14 statements out of this envelope and told me they would not have received the other 13 statements. I called the call centre several times and told them it is simply impossible that 13 other statements disappeared out of a closed envelope on the way to them, so they must search for them in their offices. All I got was always the same answer: one will look into it and get back to me, which never happened. On 14 December I called again with the same result, but this time received a reference number ( ********** 401). That was all what I received, never any other reply or settlement for the claims. This year after calling again I was told to get copies of the settlements from my doctor and send those in, which I did. I now received one email today telling me "...the claims department is unable to process your request as we received the proof of payment. Kindly email a copy of the claim..." - how many times do they need these statements in order to finally process them??? Obviously all proof of payments went to their offices with my very first submission and can not be recovered from my side, so THEY need to do their homework and find them somewhere, if not one of their staff members used the documents to wrap the lunch... Interestingly I received a second email today telling me that some of the questioned claims were received but none of them could be paid for the following reason: "We have not paid this claim because it was not submitted to us in time. You are responsible for this amount." SERIOUSLY??? Very clearly they are the ones delaying the process!!! It very much looks like the claim department tries every trick to postpone payments of claims, just to say at the end that the client submitted too late... This is definitely not the case as all was submitted originally in November, luckily with witness who can witness all above in case I have to take the matter further if not finally settled within on week. I can only recommend to stay away from Discovery until they have sorted their internal problems and procedures - the claim department is very quick with sending emails rejecting claims instead of giving service in cases like this and call the client directly in order to sort things out!