authorisation letter

I had an accident on October 2016 and I have reported my claim on the 26/10/15. It took about a month while they were telling me they still waiting for a panel beater to get the quotes and until December where I paid the excess money, and on the 11 /12/2015 they sent me an sms to tell me that the claim have been authorised and on the 05 of 01/16 I called the repairer and they said they never received a authorisation letter from Anderson insurance underwriter. I called the insurance and the person responsible linked me to the conversation they had with the repairer. and they said in 30-40 minutes they will have sent the letter. I called the repairer after two hours they said they received nothing. on the 07/01/16 I called the repairer but they said they didn't receive the letter, I called the insurance but to no avail all I get is a receptionist who took my details and said she would ask the claim department to call me. I then called again after 2-3 hours and I got a guy who said I must hold and on the background is like they were aguing with other guys for something saying\its mine