@ Harshit,
Dear Sir, each and every word in law has to be read carefully. Section 7(2)(b) does not say ANY SERVICE...but it provides "SUCH ACTIVITIES OR TRANSACTIONS UNDERTAKEN BY THE GOVT..". So far, only one activity under this section is notified i.e. the services by way of any activity in relation to a function entrusted to a Panchayat under Article 243G of the Constitution of India.
Hence, if the activity of the Government falls under article 243G, then no GST is appliable. Hence, there is no contradiction between section 7(2)(b) and section 9(3). If doubt still persists, we may discuss through whatsapp on 6380 592 749