How best can i handle customers complaints?

Reports of the accounting system and documents that prove the validity of the reports whether they are signatures or contracts or government documents or bank statements and then clarify the accounting process in a simplified way away from. scientific terms in ogical way

• 1/ Listening to the customer and show the real interesting
• 2/ Be clear and honest to win customer's trust 
• 3/ And provide solutions that are consistent with the company's policy