How to inform gst office

Radhakrishnan (Accounts Officer) (122 Points)

12 February 2021  
sir,

we are doing gst filing practicenor work. 4 years back we registered some clients with our mobile number. Address and name are there company info only. Later after 4 or 5 returns submission they discontinued from us without any intimation. now from gst office they enquired thro' our mobile and ask about the left client. The user name & pwd also doesn't know. how we will change our mobile number in that gstin portal.