Lack of motivation. I worked in support services for three different companies, and none of them would let me know what my role and value are. We were told: the customer is important, we do everything for the customers, we are a customer-focused company. We were required to follow a script under a fear of getting the low scores or having the premium cut. Nobody ever told us: guys, you are professionals, and you are doing a great job, improve your skills and be the best ones so that everyone would want to reach your level. Say it loud and clear that the customer support work is not a regular job, it's a mission, and only fulfilled individuals can offer something to others – the employees should understand their role in the company.
Things that demotivate are: lack of evaluation criteria, monotonous repetitive work, no room to express yourself, lack of prospects, and no additional trainings. Even if there is no opportunity for career growth within the company, you still can provide a professional growth. Offer them free Russian or English classes – help them learn how to use commas finally; or psychology trainings - to understand people better and learn how to work with different types of customers. Professional development motivates and increases self-satisfaction, and a happy employee will make your customers happy.