Sentences for ending a letter

• Thank you for contacting us
• Thank you for your prompt reply
• Thank you for providing the requested information
• Thank you for all your assistance
• I really appreciate any help you can provide.
• I will be grateful if you can send me this information.
• Many thanks for considering my request. (Thus acknowledging that you are grateful for the recipient to even read your email.)
• I hope what I have requested is possible. 
• In the meantime, thank you so much for your attention and participation.
• Thank you for your attention to the matter
• Thank you for your understanding