Possible Clues:

• 'At your service'
• Volunteer’s request
• 'I'm available if needed'
• 1972 No. 2 single about a manipulative lover
• 'I volunteer!'
• "I'd like to help"
• Bill Withers smash
• 'I'm here at your disposal'
• 'I'll do whatever you ask'
• Funk hit / for Bill / Withers