The best way to dealing with customer relations problems is to prevent them from happening.
There are three key ways of doing that:
1. Match the Product to the Customer
Make sure the customer knows what the product is designed to do and what it is not designed to do, and that it meets his or her needs.
Pharmay Assistant training equips you well for this.
2. Educate Your Customers in Using the Product
This is vitally important - as you cannot rely on the customer reading (or understanding) the instructions.
Educating customers is also part of the ethics of all Pharmacies.
3. Keep Your Promises
Failure to keep promises is, by far and away, one of the largest causes of customer dissatisfaction.
If you said you would order something in and have them in by Wednesday, make sure it happens.
If it is not going to happen for reasons out of your control - call the customer, apologise, and explain the revised schedule or how you are going to make it right.