GSTIN cancellation issue

I have not filed gst return since 01.01.2018. My registration status is active. GSTIN is no more required for me as my turnover is very less.

I am unaware of my user ID and PW. My professional has not shared any of such information. The mobile no. and email ID registered in portal are not of mine.

What should I do ??
How I will cancel the registration ??
Is there any late fee or tax liability will come upon me??