Every month 20% of the basic salary is added into provident fund maintained and retained by company in a bank account. After completion of six months/12 months some increase in one's provident fund amount was reported after the said period? Is this OK for us from Qur'an and Sunnah?

Praise be to Allah, the Lord of the World; and blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions.

Basically, depositing money in usury taking banks without dire necessity is not permissible.
Therefore, in such case you are not permitted to use the interest given to you on your deposited money. You are to take only your capital. But, what is added to your capital is pure interest. You should not use it at all.
However, do not leave the interest in the bank. It is better to take it and give to poor or needy Muslims or to spend it in the interest of Muslim public.
Allah knows best.