Please note that the liability to pay service tax on GTA is shifted on the service receiver, vide notification no. 30/2012 ONLY if the person liable to pay freight is:-
(a) any factory registered under or governed by the Factories Act, 1948 (63 of 1948);
(b) any society registered under the Societies Registration Act, 1860 (21 of 1860) or under any other law for the time being in force in any part of India;
(c) any co-operative society established by or under any law;
(d) any dealer of excisable goods, who is registered under the Central Excise Act, 1944 (1 of 1944) or the rules made thereunder;
(e) any body corporate established, by or under any law; or
(f) any partnership firm whether registered or not under any law including association of persons;
So if you are covered above and also liable to pay freight, then only you have to pay service tax. Otherwise say, if you are a proprietorhsip firm who is not registered under central excise, then the tax shall be paid by the GTA. If you are not paying nor liable to pay freight, then also no tax liability on you.