Gst applicability

We are a small guest house in Delhi with no branches, with turnover under Rs. 20 lakh. We host people from all over India & abroad who pay us money through cash or cheque or credit card. Would we be liable to GST. The guests are coming from outside Delhi sometimes sending advance money from their cities before coming. Would this amount to interstate sale & make us liable to GST even though we are below Rs. 20 lakhs.