Hollard Terms and conditions change when it suits them

We are a repairer and were given the authorisation to repair. We did the repair the client signed he was happy now all the terms and conditions have changed, Because we are not on their panel nor have a vat number now we are being penalised at how much we can charge. They admitted they should have paid the client out but did not now we are fighting to get paid as well as having to forfeit the little bit of profit we would make on the repair. Every day a different person requests different paperwork and STILL NO PAYMENT. I hope that repairers have received authorisation from Hollard Insurance find out the terms and conditions before they repair otherwise they will also be cheated of their hard earned money