State-run telecom operators MTNL and BSNL have slashed national roaming charges to Re 1 for incoming calls and Re 0.40 for outgoing calls within any visiting network as part of a new post-paid plan to be launched on June 3.The monthly rental for the plan has been fixed at Rs 550. The subscribers will also get 300 minutes of free talktime for receiving calls. The call rates of Re 1 will apply after the free talktime is exhausted.Outgoing calls to networks outside the visiting state will be charged at Re 1.Both the operators are expecting 20-25% jump in their traffic from this scheme.Telecom Minister A Raja had earlier said his department was looking at the possibility of lowering the domestic roaming charges, as planned by his predecessor Dayanidhi Maran.