Tax Liability - GTA under RCM

Dear Experts please clarify my below doubts.

X (GTA) is raising the invoice on 1st January, 18 and sent the invoice copy to us in that invoice they have clearly mentioned GST will be paid by recipient as per notification no. 13/2017 Dt. 28/06/17.

Now (June, 18) we are going to account the bill and we have to pay the GST under RCM.

My doubt is whether we have to pay GST along with interest? Because Invoice has been raised on 1st January, 18. As per POT Invoice raised is earlier date and tax liability incurred on 1st January, 18.