Input refund for Online Seller

Many E Commerce Sellers have already accumulated huge Input credits due to 18% GST on commission charged by ecommerce operators. Can they claim refund of ITC as it includes ITC of Goods, Commission & Others services and Fixed Assets purchased by them (They are buying/selling goods in 5% category).
Kindly suggest refund procedure as per the latest guideline by GST concil in June-July notification .