I am terribly sorry but,
Excuse me, but...
I'm sorry to trouble you, but …; Excuse me, but ….
I must apologize.
申し訳ないこと
I really don't know how to apologize to you.
あら、申し訳ございません。
I am extremely obliged to you―overwhelmed with your goodness.
うるさくてごめん
あ、すみません。
I do not know what excuse to make.