"维护客户"用英语叫做"maintaining customers"，其来源是英语中maintain的动词形式，意思是"维护"、"保持"。
例句：
We need to focus on maintaining our current customers before we try to acquire new ones.
（我们需要先关注维护现有客户，再考虑招揽新客户。）
Our customer service team is responsible for maintaining customer relationships.
（我们的客户服务团队负责维护客户关系。）
Regular communication with customers is important for maintaining their loyalty.
（定期与客户沟通对维护客户忠诚度很重要。）