Please note that policy and posters alone would not help. As an employer, you need to train the employees on what the policy means, its application, etc.
Its important that employees are aware of the reason why the Act 2013 has been put in place and the penalties involved in reporting a false case. As an employer, you have to treat this inline with your CoC-Raising False Alarm, Complaints, etc.
Raising a false complaint damages the reputation of the alleged respondent. Therefore, it needs to be seen in that light and treated very seriously.
If case is not proved then that need to be taken seriously. Action on the complainant is based on the policy, ICC can not hold the voice here. If no specific policy drafted then move it to LC or draft fine one and publish. This may help stop building the false complaints.