Airtel — heavy mnp charges

Address:

Nashik, Maharashtra, 422009

I went to airtel store in nasik (Mh) for mnp (On 13th march 2018) & was asked to pay rs.50/- for mnp & that too in cash only. As per my knowledge, trai has slashed mnp charges from 31 january 2018 to rs4/-. Mnp charges are only rs.4/-, however i asked that will i get any receipt or balance in my ac, they simply said no. Will anyone let me know why airtel is charging huge fees for mnp?