That is what my question. Taxpayer applies for Regn. and gets ARN. However the portal says to contact jurisdictional Range Officer even without allotting a GSTIN
When u file registration application, application automaticaly be shown on the related authorty GST profile by the business place you enterd in the registration applicaion .
related jurisdiction specifies by the address of business place. there is jurisdictional pdf file on VAT system of every taxation website . check the related business place in that file. and then contact to related officer of that jurisdiction.
although 3 days deadline is fixed to give SCN by related officer otherwise registration will be deemed approved. if related authority issue SCN then reply it through your GST login.