Registration in different state under gst

Our company is Service Provider & provides services under category Supply of Tangible Goods Service. We have only registered office premises in Mumbai, Maharashtra however we provides services all over India in customers premises. We have taken registration of GST at our Mumbai Office address. We don't have any branch or other premises in India. Our query is as GST is destination based tax. So shall we have to take registration of GST in each & every state where we are providing services? if Yes then on what basis we can take registration as we don't have any establishment in our name. & if No then what tax we have to charge on Interstate Supply of Service