How to file online the provisional gstin

My company is registered under GST, because we were previous registered under VAT and Luxury Tax, but our annual turnover is below 20 lakh and because of that registration is not required.

I found the following information on CBEC website: regarding cancellation of a provisional GST registration:

Rule 24 (see ad1) and  FORM GST REG-29 (see ad 2) on the CBEC website: https://www.cbec.gov.in/resources//htdocs-cbec/gst/notfctn-3-central-tax-english.pdf;jsessionid=DE159A26582ABDFF3C7D768B564EDB90   (attached)

1. Rule 24, point 4:  (4) Every person registered under any of the existing laws, who is not liable to be registered under the Act may, within a period of thirty days from the appointed day, at his option, submit an application electronically in FORM GST REG-29 at the common portal for the cancellation of registration granted to him and the proper officer shall, after conducting such enquiry as deemed fit, cancel the said registration.
2. Form GST REG-29 [See rule 24(4) ] on second to last page of the document.

So, it is clear that we can cancel our provisional GST registration before 31st July 2017 because, we were previus registered under VAT and Luxury Tax, but our annual turnover don,t exceeds Rs. 20 lakh per year..

MY QUESTION:

How to file form GST REG-29, to cancel our provisional GST registration, online? 

When I go to the common portal  " www.gst.gov.in ",   I can not find any link or help where I can file electronically this form  GST REG-29.  

Even when I visit this GST portal as a registered user, nowhere I can find anything about the cancellation procedure.

Also on your site " https://www.cbec.gov.in " I can not find any link where I can file electronically this form  GST REG-29.  

I searched in all different ways, on internet, to find the way how to file form  GST REG-29 online, but all the hints I found  are the same as I is shown here above.

I asked this question also to the GST helpdesk (helpdesk @ gst.gov.in ) 5 day ago,  but no reply til now.

Please, advice how to cancel our provisional GST registration online on the common portal.