Company offered show cause notice with false allegations

Hi , I am working a Manager from last 4 years with Company ABC. Recently two months back ABC legal and HR called with for a meeting with no agenda and started introgating about the claimed bills in ABC system and showed some bills saying this is fake or re-created bills, to which I was truely unware and asked for some time as some of the bills of food claim are given to me by my supervisor or team members and i need to talk to them or inquire with them, but the investigator clearly denh and harassed me to give in writing that act is done by me on plain paper or will terminate . Wordings where also by him. After that he asked me to resign or face inquiry. i said i will face inquiry as my mind know i am not guilty. now after 2 month's they have sent me a show cause notice with some allegations. I myself have inquired the allegations points with all respective hotels and found there is no fake bills. Also i replied with all the facts. But i doubt company may believe and may take action. HR panel also says dont send reply by email but hand to HR. I handed and then again sent by email also. Please guide me as I am honest and got stucked with no reasons. If any more details required ready to show Note : company is leading IT company