先日の件で御社に対して無礼をしてしまったことを大変申し訳無く思うとともにお詫び申し上げます。
私も御社との取引はこれが初めて不安な点もありでいろいろな事に過剰に心配をしてしまった事をご理解頂ければ幸いです。
また上記の中で御社の信頼を著しく傷つけてしまったのであれば心よりお詫び申し上げます。
大変申し訳ございませんでした。
As it is my first time to carry out the business with your company, I was concerned about some respects and worried about many matters too much. I hope that you understand it.
If I damaged trust of your company in the above matter remarkably, I deeply apologize to you.
I apologize to you again.
It would be appreciated if you would take into account that I was too anxious about and overreacted various matters as this is the first time for me to have business with you.
I felt deeply sorry if I have undermined your trust.
Please accept my sincere apology.
Second sentence alternate translation:
As this is also the first time doing business with your company, there may be excessive worries on various things. I would appreciate it if u could understand my situation.
Third sentence alternate translation
また上記の中で御社の信頼を著しく傷つけてしまったのであれば心よりお詫び申し上げます。
Moreover, we sincerely apologize if we have jeopardize the trust between our company