Perhaps, maybe you knew this phrase "Sorry, but…".
I hope I could introduce some expressions to you that they more polite than above.
"I beg your pardon/time?"
You knew the sentence 'cos I used this one in my music lyrics.
To put it differently an another sentence like below,
This phrase is used to call to somebody when the people are doing something.
And , "Pardon me" is more polite than "Excuse me".
And then, their sentences very polite ways how to call somebody whom are busy at the time.
"Can I interrupt for a moment?"
"May I interrupt for a moment?"
"I'm sorry to interrupt you."
But……you are allowed only to say "Hi!" ……in some cases.