2) Never Apologize
Not everyone will agree with this premise, but my experience is that using the word "sorry" will make you look weak. Apologizing puts you on the defensive and gives the client the upper hand, so it’s best not to backpedal.
Even in situations where your company has made a blatant mistake, there are better ways to recover than immediately dropping the S-word.
Instead of this: “I’m greatly sorry for 'fill in the blank.' I promise it will not happen again.”
Say this instead: “It’s unfortunate that 'fill in the blank' happened. My team is aware of how it affected your business, and we thank you for your patience and understanding while we resolve the matter.”
Notice the second option uses the word “unfortunate” to acknowledge remorse and uses the words “patience” and “understanding” to plant a psychological seed in the client’s mind. Even if the client hasn't been patient or understanding, using these words can reverse the tension.