It is always a bad practice to give partial information as it may result in you getting a wrong answer.
An employee can be exempt from PF only if he does not have an existing PF Account (current or from previous employer) and his starting salary when he joins the organisation is above ₹ 15,000
both conditions must be fulfilled simultaneously.
Therefore, if you join an organisation with a lower salary but it increases to 15,000 later, you will need to continue with PF. Similary, if the new join has an existing PF account, then PF continues.
In case of voluntary contribution, either party can reduce their contribution at any time. It is not necessary that other party should also stop or reduce simultaneously