SANI car rental SAGA - on repeat

I have just booked a rental care on the site. I completed the details required and when I received the confirmation from SANI my name, address and email address were incorrect. I call and asked for it to be amended and spoke to someone who said they had 'amended' it and when I received the confirmation some of the details had been amended and some that were correct were now incorrect. I have spent time on the phone to request that this be changed and was told that this was not possible without cancelling the contract and re-doing it. This happened to me before with them and it caused a great deal of inconvenience as there was a cross border letter which had incorrect details on it............. Really SANI - surely you can do better