Greetings, My name is and i am an authorize re seller of domain names

recently there were some unauthorise activity happening in my reseller account and when we investigated we found that one of our customer have initiated it so we highlited this to our parent registrar and on further investigation it was found that there was an internal employee of the registrar involved with our customer in this activity .the parent registrat terminated that employee now we are planning to take legal action against all the three our customer. the parent registrar and the employee of the registrar involved in this as all the systems of the parent registerar were used and a proper procedure was not followed by the company employee kindly let us know how we go about it.