Examples:

• That's very generous of you, but no, thank you.
• So thank you for the interest, but, no, thank you.
• That's very kind of you, but no, thank you.
• Which I've already tried today, and no, thank you.
• I'm flattered by your proposal, but no, thank you.
• I appreciate the offer, but at least for Daphne, no, thank you.
• But not in this case, no, thank you.
• Well, thanks for the offer, but, no, thank you.