A Long Response Time
A customer needs to be reassured that their concern(s) is/are important to an organization. Whenever a customer contacts the business, responding to their request in a short period of time proves to them that they are considered a valuable part of the business. Customers are the lifeblood of any business and whether they contact the business via phone, texts (sms), website, emails, WhatsApp or social media channels, processes must be in place to respond within an expected reasonable time.
If you have taken long to respond to the customer, you will have to apologize to them for taking much of their time. After that attend to them as required.