Using employees will probably be expensive but it’s sometimes worth it. For instance an employee will be able to action a complaint a lot quicker and provide the personal touch to a dissatisfied customer where an automated system cannot.
Automated customer feedback systems have a lot of benefits: they’re inexpensive to operate, they ensure consistency (every customer is asked the same question in the same way, relevant to their purchase) and it frees up your employees to focus on core tasks. However, there are times when only a human being will do.
The best approach may be to use an automated system in the first instance to gather your data, but use a trigger to alert your staff (or yourself) to cases of dissatisfaction. Get an employee to follow up all these cases to make sure they’re resolved.