Although this is a normal thing, after all, everyone's brain capacity is not so large that it is impossible for everyone to remember their names, but for customers, it is a very disrespectful behavior, but at least at this time you can remember her surname, and then in this case, you can use her surname instead of her name. For example, your customer is a woman surnamed Zhao.
Secondly, this kind of customer is usually a customer in the company. In most cases, you are just a small clerk who is responsible for talking, so many people in the company know his name. At this time, you can pick up your WeChat and ask your colleague for help. I believe that if you are fast, you can know his name in less than 3 seconds, and then you can have the next conversation.
Of course, you don't need to be too formal. If you can't remember other people's names, you won't be sentenced to death, or this business will be ruined. If this customer is enthusiastic and unrestrained, I think you can show him the dilemma that you don't know his name in a joking way. I believe he will tell you his name enthusiastically and will tease you if he is naughty enough.
But then again, this kind of low-level mistakes should be made less in the workplace. I say that before you go to see another customer, you should at least take some time to get a detailed understanding of the customer's information. It can be said that this is not a very troublesome thing, and your profound understanding will make you more topical when talking.